The scientific cooperation of the Boreskov Institute of Catalysis with the catalytic communities from various countries is effected in accordance with various forms of cooperation: conducting joint seminars on catalysis, exchanging the information and appropriate materials, exchanging research fellows, visiting scientific centers, and participating in congresses and symposia on theoretical and applied catalysis.
According to research programs, projects and grants, the fundamentals of catalysis are studied jointly with researchers from various universities, institutions, research laboratories and companies. BIC collaborates fruitfully on a commercial basis with the leading companies from more than 20 countries, sells licenses, know-how and performs research projects according to client requests.
Academician Valentin N. Parmon is the Russian representative in the European Federation of Catalytic Societies (EFCATS), Member of the International Association of the Catalysis Societies (IACS).
Austria | 2 | Germany | 26 | South Korea | 3 |
Belarus | 3 | Greece | 11 | Saudi Arabia | 6 |
Belgium | 2 | Ireland | 1 | Spain | 5 |
Bulgaria | 1 | Israel | 5 | Switzerland | 2 |
Brazil | 2 | Italy | 15 | Tunisia | 1 |
China | 9 | Japan | 6 | Turkey | 2 |
Cyprus | 1 | Kazakhstan | 1 | Ukraine | 5 |
Czechia | 1 | Netherlands | 13 | United Kingdom | 7 |
Finland | 22 | Poland | 2 | USA | 13 |
France | 16 | Portugal | 2 |
Visits of foreign specialists to the Boreskov Institute of Catalysis in 2007
Bulgaria | 1 | Italy | 5 | South Korea | 8 |
Finland | 1 | Japan | 8 | United Kingdom | 1 |
France | 4 | Kazakhstan | 4 | USA | 29 |
Germany | 1 | Netherlands | 10 |
ITALY
The cooperation in the frame of the agreement between Russian Academy of Sciences (RAS) and National Council on the Scientific Research of Italy:
FRANCE According to the agreement between RAS and CNRS BIC collaborates with:
INDIA
In the frame of Indo-Russian Integrated Long Term Programme of cooperation in science and technology (ILTP) BIC collaborates with:
• Indian Institute of Chemical Technology, Hyderabad, on the Project “Study and Development of Heterogeneous Photocatalytic Removal of Hazardous Compounds
from Air and Water”. Coordinators: Dr. A. Vorontsov (BIC) and Dr. M. Sabramaniam (Indian Institute of Chemical Technology).
• National Chemical Laboratory, Pune on the Project “Design of Bifunctional Supported Non-Iron Catalysts for Low Temperature Ammonia Synthesis”.
Coordinators: Dr. B. Moroz (BIC) and Dr. A.V. Ramaswamy (National Chemical Laboratory).
Coordinators on the Program “Catalysis” are Acad. V. Parmon and Dr. S. Sivaram.
POLAND
In the frame of RAS-PAS agreement BIC cooperates with:
GERMANY
The cooperation in the frame of the agreement between RAS and German Scientific Research Society (GSRS) with
The cooperation with J. Heyrovského Ústav Fyzikální Chemie AV ČR (J. Heyrovsky Institute of Physical Chemistry ASCR) on the Projects
CHINA
The cooperation in the frame of Associated Research Laboratory which was established by an agreement signed December 4, 2004 by the Boreskov Institute of Catalysis and Heilundzyan University, Harbin. Chief Executive officers of Laboratory are:
Prof. V. Bukhtiyarov (BIC) and Fu Hong-Gang (Heilundzyan University) on the Project
“Synthesis and Modification of ZSM-12 Zeolites. Zeolite ZSM-12 in Reaction of Naphthalene Alkylation with Methanol”. Coordinators: Prof. G.J. Sheng (Heilundzyan University), Prof. G. Echevsky (BIC).
SPAIN
The cooperation with Instituto de Catalisis y Petroleoquimica (Institute of Catalysis and Petroleochemistry), Madrid on the Project “Fundamental and Technical Aspects of in situ Spectroscopic Studies of Oxide Catalysts”. Coordinators: Prof. O. Lapina (BIC) and M.A. Bañares (Instituto de Catalisis y Petroleoquimica).
COOPERATION IN THE FRAME OF PROJECTS FINANCED BY INTERNATIONAL FOUNDATIONS
INTAS SUPPORTED PROJECTSI. Novel Catalytic Process for Industrial Waste Water Treatment < /p>
Project Coordinator:
Dr. P. Gallezot, Institut de Recherches sur la Catalyse, Villeurbanne, France Participants:
Participants:
Acad. V. Parmon, The Boreskov Institute of Catalysis, Novosibirsk, Russia
Prof. B. Laskin, Research Scientific Center for Applied Chemistry, St. Petersburg, Russia.
II. Competitive Hydrogen from Agro-Forestry Residues
Project Coordinator:
Prof. G. Grassi, European Biomass Industry Association (EUBIA), Brussels, Belgium
Participants:
Prof. V. Kirillov, The Boreskov Institute of Catalysis, Novosibirsk, Russia.
III. Sustainable Route to the Generation of Synfuels via Syngas Derived from Biomass
Project Coordinator:
Prof. J. Ross, University of Limerick, Limerick, Ireland
Participants:
Dr. K. Seshan, Universiteit Twente, Enschede, The Netherlands
Dr. O. Hazewinkel, Techno Invent Ingenieursbureau voor Milieutechniek b.v., Zoetermeer, the Netherlands
Prof. V. Sadykov, The Boreskov Institute of Catalysis, Novosibirsk, Russia
Prof. A. Rozovskii, Topchiev Institute of Petrochemical Synthesis, Moscow, Russia.
INTAS - SB RAS Supported Project
Electromagnetic Response Properties of Carbon Onions and Carbon Onion-Based Composites
Project Coordinator:Participants:
Belarus State University, Minsk, Belarus; University of Joensuu, Finland; Institute for Technical Physics and Materials Science, Budapest, Hungary; The Boreskov Institute of Catalysis, Novosibirsk, Russia (Dr. V. Kuznetsov), Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia.
EUROPEAN COMMUNITY SIXTH FRAMEWORK PROGRAM
I. International Partnership for a Hydrogen Economy for Generation of New Ionomer Membranes
Coordinator:
Dr. R. Mallant, Energy Research Centre of The Netherlands, Petten, The Netherlands
Partners:
Daimler Chrysler; FuMA-Tech GmbH; CNRS Montpellier; Dohgyue Chenzhou New Materials Company; Shanghai Jiao Tong University, Shanghai, China; The Boreskov Institute of Catalysis, Novosibirsk, Russia (Prof. V. Bukhtiyarov).
II. Co-Processing of Upgraded Bio-Liquids in Standard Refinery Units
Coordinator:
Dr. Y. Solantausta, VTT Processes, Espoo, Finland
Partners:
Rijksuniversiteit Groningen, The Netherlands; The Boreskov Institute of Catalysis, Novosibirsk, Russia (Prof. V. Kirillov); Uhde Hochdrucktechnik GmbH, Germany; BTG Biomass Technology Group BV, The Netherlands; University of Twente, The Netherlands; STFI-PACKFORSK AG, Sweden; Institute of Wood Chemistry, Hamburg, Germany; Slovenian Institute of Chemistry, Slovenia; Arkema SA, France; Helsinki University of Technology, Finland; ALMA Consulting Group SAS, France; Centre National de la Recherche Scientifique, France; Chimar Hellas SA, Greece; Albermarle Catalysts Company BV, The Netherlands; Metabolic Explorer, France; Shell Global Solutions International, The Netherlands.
III. Non-Noble Catalysts for Proton Exchange Membrane Fuel Cell Anodes
Coordinator:
Dr. G. Tsotridis, Institute for Energy, Joint Research Centre, Petten, The Netherlands
Partners:
Technical University of Denmark, Lyngby, Denmark; The Boreskov Institute of Catalysis, Novosibirsk, Russia (Acad. V. Parmon); Southampton University, United Kingdom; Technical University of Munich, Germany; Bavarian Center for Applied Energy Research; Umicore, AG & Co KG, Germany.
IV. Novel Materials for Silicate-Based Fuel Cells
Coordinator:
Dr. Ch. Arguirusis, Technische Universität Clausthal, Clausthal, Germany
Partners:
University of Aveiro, Aveiro, Portugal; Foundation of Research and Technology Hellas, Greece; Katholieke University of Leuven, Belgium; Max-Plank Institute of Colloids and Interfaces, Munchen, Germany; The Boreskov Institute of Catalysis, Novosibirsk, Russia (Prof. V. Sadykov); Ceramics and Refractories Technological Development Company, Greece; Ceramiques Techniques et Industrielles, France.
NATO PROGRAMME: SCIENCE FOR PEACE
I. Solid Oxide Fuel Cells for Energy Security
NATO Country Project Director:
Prof. N. Orlovskaya, Drexel University, Philadelphia, United States
Partner Country Project Director:
Prof. O. Vasiliev, Frantcevych Institute for Problems of Material Science, Kiev, Ukraine
Project Co-Directors:
Prof. V. Sadykov, The Boreskov Institute of Catalysis, Novosibirsk, Russia
Prof. J. Irvine, University of St. Andrews, St. Andrews, United Kingdom
Prof. N. Sammes, University of Connecticut, Storrs, United States
Prof. R. Hasanov, Azerbaijan State Oil Academy, Baku, Azerbaijan
Dr. A. Schokin, State Committee for Energy Saving of Ukraine, Kiev, Ukraine
Prof. John Kilner, Imperial College, London, United Kingdom.
II. Mixed Conducting Membranes for Partial Oxidation of Natural Gas to Synthesis Gas
NATO Country Project Director:
Prof. J. Frade, Departamento de Engenharia Cerâmica e do Vidro, Universidade de Aveiro, Aveiro, Portugal
Partner Country Project Director:
Dr. V. Kharton, Institute of Physicochemical Problems, Belarus State University, Minsk, Belarus
Project Co-Directors:
Dr. J. Irvine, School of Chemistry, University of St. Andreas, Scotland, United Kingdom Dr. T. Norby, SMN, Universitetet i Oslo, Oslo, Norway Dr. J. Jurado, Instituto de Cerámica y Vidrio, CSIC, Madrid, Spain Prof. V. Sobyanin, The Boreskov Institute of Catalysis, Novosibirsk, Russia Prof. V. Kozhevnikov, Institute of Solid State Chemistry, Ekaterinburg, Russia Dr. L. Boginsky, Institute for Personal Development and Staff Retraining in New Areas of Techniques, Technologies and Economics of the Belarus Ministry of Education, Minsk, Belarus.
NATO PROGRAMME: SCIENCE FOR PEACE AND SECURITY
Capture and Decontamination of Chemical & Biological Agents by Novel Catalysts and Millisecond Jet Reactors
Project Coordinator from a NATO Country:
Prof. P. Smirniotis, University of Cincinnaty, Cincinnaty, United States Project Coordinator from a Partner Country: Dr. A. Vorontsov, The Boreskov Institute of Catalysis, Novosibirsk, Russia.
Project Coordinator from a NATO Country:
Dr. M. Banares, Instituto de Catalisis y Petroleoquimica, Madrid, Spain Dr. M. Ziolek, Adam Mickieiwcz University, Poznan, Poland Project Coordinator from a Partner Country: Prof. O. Lapina, The Boreskov Institute of Catalysis, Novosibirsk, Russia.
INTERNATIONAL SCIENCE AND TECHNOLOGY CENTER (ISTC)
I. Development of Catalysts and Reactors for Syn-Gas Production from Diesel Fuel and for Selective NOx Reduction with Syn-Gas in Diesel Exhausts Project Manager from BIC Prof. V. Kirillov.
II. Development of High-Performance Oxygen-Containing Membranes and Compact Syn-Gas Generators on Their Base
Project Manager from BIC Prof. V. Sadykov.
III. Synthesis and Investigation of the Metal Oxide Catalysts for Photocatalytic Degradation of Harmful Gases Resulted from Terrorist Acts and Man-Caused Catastrophes
Project Manager from BIC Dr. A. Vorontsov.
IV. Catalytic Production of SO3 for Conditioning of Electrostatic Precipitators Using in Russia and the Newly Independent States (NIS)
Project Manager from BIC Prof. A. Zagoruiko.
V. Development of an Integrated Separator for Direct Reforming of Hydrocarbons in High-Temperature Fuel Cells
Project Manager from BIC Prof. Z. Ismagilov.
A COMPUTATIONAL STUDY OF H2 DISSOCIATION ON SILVER SURFACES: THE EFFECT OF OXYGEN IN THE ADDED ROW STRUCTURE OF Ag(110)
A.B. Mohammad*, K.H. Lim*, I.V. Yudanov, K.M. Neyman*, N. Rösch* (*Technische Universität München, Garching, Germany)
Phys. Chem. Chem. Phys. 9(10) (2007) pp. 1247-1254.
The activation of H2 on clean planar (111), (110) and stepped (221) as well as oxygen pre-covered silver surfaces using a density functional slab model approach was studied computationally. In line with previous data clean silver was determined to be inert towards H2 dissociation, both thermodynamically and kinetically. The reaction is endothermic by approximately 40 kJ mol-1 and exhibits high activation energies of approximately 125 kJ mol-1T>. However, oxygen on the surface, modeled by the reconstructed surface p(2x1)O/Ag(110) that exhibits -O-Ag-O-added rows, renders H2 dissociation clearly exothermic and kinetically feasible. The reaction was calculated to proceed in two steps: first the H-H bond is broken at an Ag-O pair with an activation barrier Ea approximately 70 kJ mol-1, then the H atom bound at an Ag center migrates to a neighboring O center with Ea approximately 12 kJ mol-1.
MECHANISM OF OLEFIN EPOXIDATION WITH TRANSITION METAL PEROXO COMPLEXES: DFT STUDY
I.V. Yudanov
J. Struct. Chem., supply_48 (2007) pp. S111-S124.
Using density functional calculations over the last decade led to considerable progress in understanding the mechanism of olefin epoxidation with Ti, V, Mo, W, and Re peroxo complexes. According to calculations, the reaction occurs by direct electrophilic transfer of one of the atoms of the peroxo group to the olefin. The alternative stepwise mechanism, which has been discussed for a long time and suggested the formation of a metallocyclic intermediate, is characterized by higher activation barriers than direct transfer. The electrophilic character of the direct transfer of oxygen was interpreted at the level of molecular orbital analysis as interaction between the HOMO of the olefin π(C-C) and the LUMO of the peroxo group σ*(O-O). The factors determining the activity of various metal complexes in epoxidation were examined in relation to the ligand environment and the structure of the peroxo group.
ELECTRONIC STRUCTURE AND BONDING OF {Fe(PhNO2)}6 COMPLEXES: A DENSITY FUNCTIONAL THEORY STUDY
O. Isayev*, L. Gorb*, I.L. Zilberberg, J. Leszczynski* (*Jackson State University, Jackson, USA)
J. Phys. Chem. A, 111(18) (2007) pp. 3571-3576.
Reduction of nitro-aromatic compounds (NACs) proceeds through intermediates with a partial electron transfer into the nitro group from a reducing agent. To estimate the extent of such a transfer and, therefore, the activity of various model ferrous-containing reductants toward NAC degradation, the unrestricted density functional theory (DFT) in the basis of paired Lowdin-Amos-Hall orbitals has been applied to complexes of nitrobenzene (NB) and model Fe(II) hydroxides including cationic [FeOH]+, then neutral Fe(OH)2, and finally anionic [Fe(OH)3]-. Electron transfer is considered to be a process of unpairing electrons (without the change of total spin projection Sz) that reveals itself in a substantial spin contamination of the unrestricted solution. The unrestricted orbitals are transformed into localized paired orbitals to determine the orbital channels for a particular electron-transfer state and the weights of idealized charge-transfer and covalent electron structures. This approach allows insight into the electronic structure and bonding of the {Fe(PhNO2)}6 unit (according to Enemark and Feltham notation) to be gained using model nitrobenzene complexes. The electronic structure of this unit can be expressed in terms of π-type covalent bonding [Fe+2(d6, S = 2) - PhNO2(S = 0)] or charge-transfer configuration [Fe+3(d5, S = 5/2) - {PhNO2}-((π*)1, S = 1/2)].
DENSITY FUNCTIONAL THEORY STUDIES OF NITROUS OXIDE ADSORPTION AND DECOMPOSITION ON Ga-ZSM-5
V.N. Solkan*, G.M. Zhidomirov, V.B. Kazansky*
(*Zelinsky Institute of Organic Chemistry, Moscow, Russia)
Int. J. Quantum Chem., 107(13) (2007) pp. 2417-2425.
In this study, density functional theory (DFT/B3LYP) was used to assess a possible reaction pathway for the catalytic dissociation of N2O. The active centers were taken to be mononuclear [Ga]+ and [Ga=O]+, and the surrounding portion of the zeolite was represented by a 3T cluster, namely (AlSi2O4H8). The first step of N2O decomposition involves the formation of [GaO]+ and the release of N2. The metaloxo species produced in this step then react with N2O again, to release N2 and form GaO2. The calculated activation energies for N2O dissociation in Ga-ZSM-5 and GaO-ZSM-5 at B3LYP/6-31+G* level are 22.2 and 24.9 kcal/mol, respectively. The calculated energy of the molecular oxygen elimination from 3T-(GaO2) cluster is ΔH (298 K) = +46.5 kcal/mol and ΔG (298 K) = 35.9 kcal/mol.
SWIFT HOPPING GALLIUM [AlO4]-TETRAHEDRA IN Ga/ZSM - A DFT STUDY
I.V. Kusmin*, G.M. Zhidomirov, V.N. Solkan*
(*Zelinsky Institute of Organic Chemistry, Moscow, Russia)
Int. J. Quantum Chem., 107(13) (2007) pp. 2434-2441.
Density functional theory calculations were carried out to investigate gallium species (Ga+, [GaH2]+, and [GaO]+) stabilization in Ga-exchanged HZSM-5, using cluster modeling approach. Three isomeric gallium positions over [AlO4]- zeolite fragment at T12 position were found. These isomers are turning into each over with low activation energy barrier and gallium fragment revolves around [AlO4]tetrahedron by hopping between cationic positions. Activation energies of gallium fragment hopping were computed and compared for different gallium containing cations. Those barriers were found to be times less than the activation energies of catalytic processes on gallium-exchanged zeolite.
MODELS OF ACTIVE SITES IN SUPPORTED Cu METAL CATALYSTS IN 1,2-DICHLOROETHANE DECHLORINATION. DFT ANALYSIS
V.I. Avdeev, V.I. Kovalchuk*, G.M. Zhidomirov, J.L. d’Itri* (*University of Pittsburgh, Pittsburgh, USA)
J. Struct. Chem., supply_48 (2007) pp. S160-S170.
It is suggested that a set of discrete Cu nanoclusters satisfying the conditions of structural and electron stability should be used as models of active sites on supported metal catalysts. The close-packed Cu20 tetrahedral nanocluster that satisfies these two conditions was taken as a base model of active sites on supported copper catalysts. Theoretical analysis of two possible mechanisms of C-Cl bond dissociation of 1,2-dichloroethane on copper catalysts was performed by the density functional theory method. The first mechanism involves sequential splitting of C-Cl bonds in the molecule in three stages with further stabilization of chloroalkyl intermediates (stepwise mechanism). All these stages are activated. The limiting stage is the one that corresponds to dissociation of the first C-Cl bond with an activation energy of E# =34.3 kcal/mol. The second mechanism corresponds to the simultaneous elimination of two chlorine atoms from 1,2-dichloroethane with liberation of ethylene in the gas phase; this is a one-stage process with an activation energy of E#=26.1 kcal/mol (direct mechanism). A comparison of the two reaction routes shows that the direct mechanism is most probable on copper catalysts.
DFT ANALYSIS OF THE MECHANISM OF 1,2-DICHLOROETHANE DECHLORINATION ON SUPPORTED Cu-Pt BIMETALLIC CATALYSTS
V.I. Avdeev, V.I. Kovalchuk*, G.M. Zhidomirov, J.L. d’Itri * (*University of Pittsburgh, Pittsburgh, USA)
J. Struct. Chem., supply_48 (2007) pp. S171-S183.
The reaction routes of 1,2-dichloroethane dechlorination to ethylene on discrete nanoclusters that served as models of the active sites of supported Cu-Pt catalysts were calculated. Two reaction pathways were predicted. The first route corresponds to sequential elimination of the chlorine atoms from 1,2-dichloroethane; this is a three-stage reaction that occurs via two stable intermediates (stepwise mechanism). The limiting stage is the stage that corresponds to the dissociation of the first C-Cl bond. The second channel corresponds to a simultaneous one-stage elimination of two chlorine atoms (direct mechanism). Both reaction routes are thermodynamically possible, but the stepwise process is more probable, in contrast to the process on monometallic Cu catalysts. For the stepwise process, the vibrational spectra of stable intermediates were calculated for identification of the latter. A set of spectral data characteristic for the stepwise mechanism were determined. The three-step molecular mechanism suggested for 1,2-dichloroethane dechlorination to ethylene is compared with several kinetic schemes known from the literature. Possible modifications of the reaction route that forms ethane and monochloroethane are analyzed.
DENSITY FUNCTIONAL THEORY MOLECULAR CLUSTER STUDY OF COPPER INTERACTION WITH NITRIC OXIDE DIMER IN Cu-ZSM-5 CATALYSTS
I.I. Zakharov,Z.R. Ismagilov, S.Ph. Ruzankin, V.F. Anufrienko, S.A. Yashnik, O.I. Zakharova*
(*East Ukrainian National University, Severodonetsk, Ukraine)
J. Phys. Chem. C, 111(7) (2007) pp. 3080-3089.
The various quantum chemical models of catalytic active site in Cu-ZSM-5 zeolites are analyzed. The density functional theory (DFT) is used to calculate the electronic structure of molecular cluster (HO)3Al-O-Cu-O-Cu modeling the catalytic active site in Cu-ZSM-5 zeolites and study the interaction and decomposition of NO. It is assumed that the rate-determining stage of the low-temperature selective catalytic reduction of NO is the formation of the π-radical (N2O2)-on electron donor sites of Cu-ZSM-5 catalysts. This is in good agreement with the high electron affinity of the molecular dimer ONNO (Ea = -1.5 eV) and is confirmed by the experimental data on the formation of surface anion π-radical (N2O2)- on electron donor sites of supported organo-zirconium surface complex. The DFT calculated electronic structure and excitation energy spectra for the model system (HO)3Al-O-Cu-O-Cu show that it is a satisfactory model for description of experimental UV-vis spectra of Cu-ZSM-5, containing (-O-Cu-O-Cu-) chain structures in the zeolite channels. The calculated reaction energy profile of ONNO adsorption and decomposition on the model catalytic active site shows the possibility of the low-temperature decomposition of dimer (NO)2 with low activation energy and the important role of copper oxide chains (-O-Cu-O-Cu-) in the channels of Cu-ZSM-5 zeolite during selective reduction of NO.
DFT QUANTUM-CHEMICAL CALCULATIONS OF NITROGEN OXIDE CHEMISORPTION AND REACTIVITY ON THE Cu(100) SURFACE
I.I. Zakharov, A.V. Suvorin*, A.I. Kolbasin*, O.I. Zakharova* (*East Ukrainian National University, Severodonetsk, Ukraine)
J. Struct. Chem., supply_48 (2007) pp. S147-S159.
A DFT quantum-chemical study of NO adsorption and reactivity on the Cu20 and Cu16 metal clusters showed that only the molecular form of NO is stabilized on the copper surface. The heat of monomolecular adsorption was calculated to be ΔHm = −49.9 kJ/mol, while dissociative adsorption of NO is energetically unfavorable, ΔHd = +15.7 kJ/mol, and dissociation demands a very high activation energy, Ea = +125.4 kJ/mol. Because of the absence of NO dissociation on the copper surface, the formation mechanism of the reduction products, N2 and N2O, is debatable since the surface reaction ultimately leads to N-O bond cleavage. As the reaction occurs with a very low activation energy, Ea = 7.3 kJ/mol, interpretation of the NO direct reduction mechanism is both an important and intriguing problem because the binding energy in the NO molecule is high (630 kJ/mol) and the experimental studies revealed only physically adsorbed forms on the copper surface. It was found that the formation mechanism of the N2 and N2O reduction products involves formation (on the copper surface) of the (OadN-NOad) dimer intermediate that is chemisorbed via the oxygen atoms and characterized by a stable N-N bond (rN-N ~1.3 Å). The N-N binding between the adsorbed NO molecules occurs through electron-accepting interaction between the oxygen atoms in NO and the metal atoms on the “defective” copper surface. The electronic structure of the (OadN-NOad) surface dimer is characterized by excess electron density (ON-NO)δ− and high reactivity in N-Oad bond dissociation. The calculated activation energy of the destruction of the chemisorbed intermediate (Oad N-NOad) is very low (Ea = 5–10 kJ/mol), which shows that it is kinetically unstable against the instantaneous release of the N2 and N2O reduction products into the gas phase and cannot be identified by modern experimental methods of metal surface studies. At the same time, on the MgO surface and in the individual (Ph3P)2Pt(O2N2) complex, a stable (OadN-NOad) dimer was revealed experimentally.
QUANTUM CHEMICAL EXAMINATION OF INTERACTION OF CYTOSTATIC FLUOROURACIL WITH DEOXYRIBONUCLEIC ACIDS
G. Yuldasheva*, G.M. Zhidomirov (*Biochemistry, National Centre of Examination of Medical Products, Almaty, Kazakhstan)
Int. J. Quantum Chem., 107(13) (2007) pp. 2384-2388.
Within the framework of semiempirical method of quantum chemical PM3, the possibility of formation of paired stack structures under interaction of fluorouracil with pyrimidine and purine nitrogenous bases of nucleotides has been examined. Possible mechanism of transformation of 2-deoxyuridine-5-monophosphate into metabolite-5fluorin-2-deoxyuridine-5-monophosphate has been given. The calculations that were made allow to suppose that biotransformation of 5-FU in 5-fluorin-2deoxyuridine-5-monophosphate, most likely, is carried out not in free nucleotides, but in the structure of DNA in two nucleotide triplets UUC and UGU, including the case when directly two nucleotides of deoxyuridine monophosphate, are transformed into 5-fluorin-2-deoxyuridine-5-monophosphate.
Cytostatic ability of 5-FU is increased by its capacity to be selectively embedded into nucleotide triplets creating new chemical compounds that violate matrix RNA formation and accordingly violate protein synthesis.
CHEMICAL BONDING AND ELECTRONIC STRUCTURE OF LaMnO3 AND La0.75MnO3 ORTHORHOMBIC CRYSTALS
V.M. Tapilin
J. Struct. Chem., 48(2) (2007) pp. 212-218.
The electronic structure of the LaMnO3 orthorhombic crystal of a stoichiometric composition and of La0.75MnO3
crystals with a La vacancy in the unit cell is calculated in the LSDA+U approximation of density functional theory.
The calculations showed that LaMnO3 is an insulator with a forbidden gap of
0.5 eV and with antiferromagnetic ordering of magnetic moments. The magnetic moment on the manganese ions is 3.78 BM. The La atom has ionic bonds
in the lattice, while the bond between oxygen and manganese is covalent. After lanthanum has been removed, geometry optimization of the unit
cell leads to La0.75MnO3 stable structures.
In one of the structures, which is lower in energy, the states of manganese may be
attributed to Mn4+ ions. In both structures with removed lanthanum, the oxygen ions have reduced effective charge, so that one can speak
about O
THEORETICAL AND EXPERIMENTAL DAPS STUDY OF CLEAN, OXYGEN, AND HYDROGEN COVERED Pt(100) SINGLE CRYSTAL SURFACE
A.R. Cholach, V.M. Tapilin
Phys. Chem.: An Indian J., 2(1) (2007) 6 pages.
Local density of states is calculated for the three-fold Pt(100) slab surface covered with various coverage of hydrogen and oxygen. The formation of new surface states region below the platinum conduction band is responsible for covalent contribution to the bond formation between adsorbed species and surface Pt atoms. Resonant states around the substrate Fermi level give an ionic constituent to the adsorbate-surface chemical bond due to considerable DOS difference between adsorbed and surface platinum atoms. Calculated and experimental extended disappearance potential spectra related to different H and O coverage are in a good agreement in spite of baffling complexity of spectral structures. Remarkable similarity between theoretical and experimental results evidences for reliability of obtained data on the LDOS structure of adsorbed system considered.
V.I. Elokhin, A.V. Matveev, V.V. Gorodetskii, E.I. Latkin
Lect. Notes Comp. Sci., “Parallel Comp. Technol.”, 4671 (2007) pp. 401-409.
The dynamic behaviour of the CO oxidation reaction over Pd(110) has been studied by means of probabilistic asynchronous cellular automata (Dynamic Monte-Carlo). The influence of the internal parameters on the shapes of surface concentration waves obtained in simulations under the limited surface diffusion intensity conditions has been studied. The hysteresis in oscillatory behaviour has been found under step-by-step variation of oxygen partial pressure. Two different oscillatory regimes could exist at one and the same parameters of the reaction. The parameters of oscillations (amplitude, period and the shape of spatiotemporal patterns on the surface) depend on the kinetic prehistory of the system. The possibility for the appearance of the cellular and turbulent patterns, spiral, target and stripe oxygen waves on the surface in the cases under study has been shown.
SIMULATION OF METHANE OXIDATION ON Pt
V.P. Zhdanov, P.-A. Carlsson*, B. Kasemo*
(*Chalmers University of Technology, Goteborg, Sweden)
>J. Chem. Phys., 126(23) (2007) pp. 234705 (6 pages).
The authors present a generic model of CH4 oxidation on Pt with the emphasis on the role of surface-oxide formation. The latter process is treated in terms of the theory of first-order phase transitions. The corresponding Monte Carlo simulations indicate that the surface-oxide formation may result in stepwise features in the reaction kinetics. Specifically, with increasing CH4 pressure and/or decreasing O2 pressure, the model predicts a sharp transition from a low-reactive state with the surface completely covered by oxide to a high-reactive state with the surface covered by chemisorbed oxygen. In the former case, the reaction is first order in CH4 and zero order in O2. In the latter case, both reaction orders are positive. All these findings help in interpreting available experiments.
LIPID EXCHANGE DURING CONTACT BETWEEN OPPOSITELY CHARGED LIPID BILAYERS
Zhdanov, B. Kasemo* (*Chalmers University of Technology, Goteborg, Sweden)
J. Phys. Chem, B, 111(32) (2007) pp. 9428-9430.
The mechanistic details of processes occurring in and during contact between lipid bilayers are still poorly understood due to their complexity on the mesoscopic scale. Here, lipid exchange during contact of oppositely charged lipid bilayers is analyzed. Specifically, a generic mechanism is explored, where this process occurs via diffusion of individual lipids between the layers. The estimates indicate that this scenario is feasible on the time scale of conventional experiments and also on the time scale of biochemical processes in cells.
ENHANCEMENT OF PROTEIN ADSORPTION INDUCED BY SURFACE ROUGHNESS
K. Rechendorff*, M.B. Hovgaard*, M. Foss*, V.P. Zhdanov, F. Besenbacher* (*University of Aarhus, Aarhus C, Denmark)
Langmuir, 22(26) (2006) pp. 10885-10888.
Using quartz crystal microbalance with dissipation and ellipsometry, it is shown that during adsorption of fibrinogen on evaporated tantalum films the saturation uptake increases with increasing rootmean-square roughness (from 2.0 to 32.9 nm) beyond the accompanying increase in surface area. This increase is attributed to a change in the geometrical arrangement of the fibrinogen molecules on the surface. For comparison, the adsorption of a nearl y globular protein, bovine serum albumin, was studied as well. In this case, the adsorption was less influenced by the roughness. Simple Monte Carlo simulations taking into account surface roughness and the anisotropic shape of fibrinogen reproduce the experimentally observed trend.
KINETIC MODEL OF HIV INFECTION
V.P. Zhdanov
J. Exp. Theor. Phys., 105(4) (2007) pp. 856-860.
The recent experiments, clarifying the details of exhaustion of the CD8 T cells specific to various strains of human immunodeficiency virus (HIV), are indicative of slow irreversible (on the one-year time scale) deterioration of the immune system. The conventional models of HIV kinetics do not take this effect into account. Removing this shortcoming, it is shown the likely influence of such changes on the HIV escape from control of the immune system.
CONTROLLED RADIAL DISTRIBUTION OF NANOSCALE VESICLES DURING BINDING TO AN OSCILLATING QCM SURFACE
M. Edvardson*, V.P. Zhdanov, F. Hook** (*Chalmers University of Technology, Goteborg, Sweden; **Lund University, Lund, Sweden)
Small, 3(4) (2007) pp. 585-589.
The article contains experimental and theoretical data illustrating radial distribution of nanoscale vesicles during binding to an oscillating QCM surface.
EFFECT OF CELL-CELL COMMUNICATION ON THE KINETICS OF PROLIFERATION AND DIFFERENTIATION OF STEM CELLS
V.P. Zhdanov
Chem. Phys. Lett., 437(4-6) (2007) pp. 253-256.
A generic mean-field kinetic model describing the interplay between proliferation, differentiation, death and communication in an ensemble of stem and differentiated cells is presented. The model takes into account the influence of signals between cells on the rate and outcome of division of stem cells. The cellular growth kinetics calculated exhibit three phases, including the initial lag phase, transient exponential growth, and steady state. Due to the effect of cell-cell communication on the division outcome, the growth may be slightly non-monotonous. Under certain conditions, the model predicts stable oscillations as well.
STEM CELL PROLIFERATION AND DIFFERENTIATION AND STOCHASTIC BISTABILITY IN GENE EXPRESSION
V.P. Zhdanov
J. Exp. Theor. Phys., 104(1) (2007) pp. 162-169.
The process of proliferation and differentiation of stem cells is inherently stochastic in the sense that the outcome of cell division is characterized by probabilities that depend on the intracellular properties, extracellular medium, and cell-cell communication. Despite four decades of intensive studies, the understanding of the physics behind this stochasticity is still limited, both in details and conceptually. Here, it is suggest a simple scheme showing that the stochastic behavior of a single stem cell may be related to (i) the existence of a short stage of decision whether it will proliferate or differentiate and (ii) control of this stage by stochastic bistability in gene expression or, more specifically, by transcriptional “bursts”. Monte Carlo simulations indicate that proposed scheme may operate if the number of mRNA (or protein) molecules generated during the high-reactive periods of gene expression is below or about 50. The stochastic-burst window in the space of kinetic parameters is found to increase with decreasing the mRNA and/or regulatory-protein numbers and increasing the number of regulatory sites. For mRNA production with three regulatory sites, for example, the mRNA degradation rate constant may change in the range ± 10%.
EFFECT OF mRNA DIFFUSION ON STOCHASTIC BURSTS IN GENE TRANSCRIPTION
V.P. Zhdanov
JETP Lett., 85(6) (2007) pp. 302-305.
The positive feedback between messenger ribonucleic acid (mRNA) and regulatory-protein production may result in bistability and stochastic "bursts"' in gene transcription. The temporal kinetics of such bursts has already been simulated in detail. It is (i) shown that the applicability of the temporal models may be limited due to relatively slow mRNA and/or protein diffusion and (ii) presented the first 3D Monte-Carlo simulations indicating that, with explicit mRNA diffusion, the bursts may be much more irregular; the periods between bursts may be much shorter, and, depending on the circumstances, the burst window may be reduced or extended.
STOCHASTIC BISTABLE KINETICS OF GENE TRANSCRIPTION DURING THE CELL CYCLE
V.P. Zhdanov
JETP Lett., 84(11) (2007) pp. 632-634.
The positive feedback between messenger ribonucleic acid (mRNA) and regulatory-protein production may result in bistability of gene transcription. If in addition the mRNA and/or protein numbers in a cell are low, one can observe stochastic transcriptional “bursts” provided that the intracellular conditions are steady. Monte Carlo simulations showing what may happen with the bursts under transient conditions during the cell cycle are reported.
OSCILLATORY KINETICS OF GENE TRANSCRIPTION DURING THE CELLULAR GROWTH
V.P. Zhdanov
Techn. Phys. Lett., 86(7) (2007) pp. 563-566.
The negative feedback between mRNA and regulatory-protein production may result in oscillations in the kinetics of gene transcription. If the mRNA and/or protein number are low, the oscillations may be irregular. Mean-field calculations and Monte-Carlo simulations showing evolution of such oscillations during the cellular growth and division are presented. The oscillations are found to be fairly stable with respect to the cellular growth.
EFFICIENCY OF THE PLASMON-MEDIATED ENHANCEMENT OF PHOTOEXCITATION OF ADSORBATE ON nm-SIZED METAL PARTICLES
V.P. Zhdanov, B. Kasemo* (*Chalmers University of Technology, Goteborg, Sweden)
Chem. Phys. Lett., 433(1-3) (2007) pp. 132-135.
Photoexcitation of molecules adsorbed on a nm-sized metal particle can be appreciably enhanced due to plasmon oscillations. The price for this enhancement is characterized by the ratio of the rates of light absorption by plasmons and an adsorbed molecule. The equations are presented making it possible to estimate this ratio for monochromatic light and also in the case when the photon frequency is distributed over an interval which is wider than the plasmon damping width.
SIMULATION OF PROCESSES RELATED TO H2-O2 PEM FUEL CELLS
Zhdanov
J. Electroanal. Chem., 607(1-2) (2007) pp. 17-24. The understanding of elementary processes occurring in low-temperature H2–O2 polymerelectrolyte-membrane (PEM) fuel cells is still limited due to their complexity on atomic and mesoscopic scales. Here, Monte Carlo analysis of two related problems is presented. (i) Due to phase separation of the hydrophobic polymer chains and water, polymer electrolytes such as wetted NAFION are heterogeneous on the scale of about 10 nm and accordingly can be viewed as a porous solid filled by water. One of the physically reasonable models of such pores can be constructed using 3D Ostwald ripening of a lattice gas with attractive interactions. Employing this model, simulations of random-walk diffusion of guest particles in pores were performed. The tracer diffusion coefficient is demonstrated to rapidly decrease with decreasing porosity and near the percolation threshold to be described by the power law. The threshold porosity and the corresponding dynamic exponent are found to be 0.23 ± 0.01 and 0.82 ± 0.01. (ii) The experiments show that the kinetics of O2 reduction on Pt (with NAFION as electrolyte) is first order in O2 in a wide range of reaction conditions. In addition, there are indications that during this reaction the atomic-oxygen coverage may be appreciable. These two findings can be adjusted taking into account the effect of repulsive lateral interactions between oxygen adatoms on the reaction kinetics. The surface mobility of these atoms may be low. It is shown that the influence of the latter factor on the reaction kinetics is minor.
OSTWALD RIPENING OF CLOSE-PACKED AND HONEYCOMB ISLANDS DURING COADSORPTION
V.P. Zhdanov
Phys. Rev. B, 76(3) (2007) 033406.
To mimic the self-assembly of hexagonally shaped molecules such as cyanuric acid and melamine, Monte Carlo simulations of the growth of close-packed and honeycomb islands during adsorption and coadsorption of A and B particles on a triangular lattice are presented. Each particle occupies a single site and is characterized by its orientation on the lattice. The orientation is changed by rotation by 60 degrees, so that the rotation by 120 degrees does not change the Hamiltonian. The model predicts slow or nearly negligible island growth at t ≤ 103 Monte Carlo steps (MCSs) and then faster growth. On the late stage (105≤ t ≤ 106 MCSs), the growth exponent is found to be 0.28-0.30 in the case of adsorption of particles of one type and 0.24-0.29 in the case of coadsorption. These values are somewhat or appreciably lower than the Lifshitz-Slyozov exponent x=1/3.
KINETICS OF THE N2O-CO REACTION ON Rh(110)
V.P. Zhdanov, O. Nakagoe*, T. Matsushima* (*Hokkaido University, Sapporo, Japan)
Surf. Sci., 601(10) (2007) L49-L54.
Recent studies of the steady-state kinetics of the N2O-CO reaction on Rh(1 1 0) indicate that at CO excess, the reaction rate increases with increasing temperature. At N2O excess, the reaction rate is nearly independent of temperature at T < 520 K and rapidly decreases with increasing temperature at T > 520 K. Present analysis of the relevant data indicates that the latter feature seems to be related to surface-oxide formation. Following this line, it is proposed a mean-field kinetic model making it possible to describe and clarify the experiment.
SIMULATION OF THERMAL DESORPTION SPECTRA OF N2 OBSERVED DURING N2O DECOMPOSITION ON Rh(100)
V.P. Zhdanov, T. Matsishima* (*Hokkaido University, Sapporo, Japan)
Surf. Sci., 601(11) (2007) pp. 2373-2377.
The fulfilled measurements indicate that under temperature-programmed conditions the NO decomposition occurs on Rh(100) between 60 and 140 K and results in the appearance of two N2 desorption peaks related to N2 molecules leaving the surface during and after N2O dissociation events, respectively. Both peaks are observed even at low initial coverages. This and other features of N2 desorption are explained by using Monte Carlo simulations taking into account attractive N2O-O lateral interactions stabilizing N2O adsorption. The results presented are compared with those obtained earlier for Rh(110).
INTERPLAY OF FIRST-ORDER KINETIC AND THERMODYNAMIC PHASE TRANSITIONS IN HETEROGENEOUS CATALYTIC REACTIONS
V.P. Zhdanov, T. Matsishima* (*Hokkaido University, Sapporo, Japan)
Phys. Rev. Lett., 98(3) (2007) 036101.
Using the rate constants obtained on the basis of independent transient measurements and density functional theory calculations, Monte Carlo (MC) simulations of the bistable kinetics of the N2O-CO reaction on Pd(110) at 450 K were performed. In the absence of lateral interactions, the MC technique predicts a wide hysteresis loop in perfect agreement with the mean-field analysis. With attractive substrate-mediated lateral interactions resulting in the formation of (1 x 2) O islands and reducing the reaction rate inside islands, the hysteresis is found to be dramatically (about 5 times) narrower. This finding explains why the first-order kinetic phase transition experimentally observed in this reaction is not accompanied by hysteresis.
CRITERION FOR EXTINCTION OF CO OXIDATION IN A CATALYTIC MONOLITH
V.P. Zhdanov
Catal. Lett., 116(1-2) (2007) pp. 23-26.
The extinction of CO oxidation occurring on the Pt catalyst in a monolithic reactor depends on the interplay of the reaction kinetics and mass and heat transfer. In particular, it may be related to a first-order kinetic phase transition from the high-reactive regime to the low-reactive regime. For this scenario, the criterion for extinction are obtained.
SIMULATION OF THE EFFECT OF SURFACEOXIDE FORMATION ON BISTABILITY IN CO OXIDATION ON Pt-GROUP METALS
V.P. Zhdanov
J. Chem. Phys., 126 (2007) 074706 (9 pages).
The kinetics of CO oxidation on Pt-group metals are known to often exhibit bistability. During the low-reactive regime observed at relatively high CO pressure, the surface is primarily covered by CO and the reaction rate is controlled by O2 dissociation. During the high-reactive regime at relatively low CO pressure, in contrast, the surface is mainly covered by oxygen and the reaction rate is proportional to CO pressure. In the latter case, the adsorbed oxygen may be in the chemisorbed state and/or may form surface oxide. The experiments indicate that the formation of surface oxide often occurs via the island growth and accordingly should be described in terms of the theory of first-order phase transitions. Here, the author proposes a generic lattice-gas model satisfying this requirement and allowing one to execute the corresponding Monte Carlo simulations. Systematically varying the model parameters determining the oxide stability, he classifies the likely scenarios of the bistable reaction kinetics complicated by oxide formation.
KINETIC EXPLOSION AND BISTABILITY IN ADSORPTION AND REACTION OF ACETIC ACID ON Pd(110)
M. Bowker*, C. Morgan*, V.P. Zhdanov (*School of Chemistry, Cardiff University, Cardiff, UK)
Phys. Chem. Chem. Phys., 9(42) (2007) pp. 5700-5703.
The adsorption and reaction of acetic acid with Pd(110) have been studied using thermal molecular beam reaction measurements and temperature-programmed desorption. Acetic acid adsorption results in the formation of acetate species which decompose to produce coincident CO2 and H2 desorption from the surface. C is deposited on the surface from the dehydrogenation of the methyl group. In combination, these steps are found to exhibit unusual kinetics including (i) a “surface explosion” during heating and (ii) bistability in the reaction profile for heating and cooling curves. This is the first report of such behaviour for a complex system during in situ reaction.
THREE-DIMENSIONAL MONTE CARLO SIMULATIONS OF INTRACELLULAR DIFFUSION AND REACTION OF SIGNALING PROTEINS
V.P. Zhdanov
J. Chem. Phys., 127 (2007) 035101 (4 pages).
It is shown that the Monte Carlo technique makes it possible to perform three-dimensional simulations of intracellular protein-mediated signal transduction with realistic ratio of the rates of protein diffusion and association with genes. Specifically, it is illustrated that in the simplest case when the protein degradation and phosphorylation/dephosphorylationthe are negligible the distribution of the first passage time for this process is close to exponential provided that the number of target genes is between 1 and 100.
BORESKOV-HORIUTI-ENOMOTO RULES FOR REVERSIBLE HETEROGENEOUS CATALYTIC REACTIONS
V.P. Zhdanov
Surf. Rev. Lett., 14(3) (2007) pp. 419-424.
In the middle of the previous century, G.K. Boreskov and independently J. Horiuti and S. Enomoto showed that for reversible reactions, running via a one-route mechanism with a rate-limiting step, there exist general relationships between the reaction rates in the forward and backward directions and also between the corresponding apparent activation energies and reaction heat. Their treatments are formally applicable to gas- and liquid-phase reactions and also to heterogeneous catalytic reactions (HCR) occurring in an ideal overlayer adsorbed on a uniform surface. In reality, HCR often run on heterogeneous surfaces and the HCR kinetics are complicated by adsorbate-adsorbate lateral interactions. It is explicitly demonstrated that in such situations the Boreskov-Horiuti-Enomoto rules are applicable as well.
V.I. Bukhtiyarov
Russ. Chem. Rev., 76(6) (2007) pp. 553-581.
A fundamental approach to the development of heterogeneous catalysts consisting of the study of the structure–activity relationships using surface science methods and techniques is proposed. According to this approach, a study should start with an investigation into well-ordered single crystals under ultrahigh vacuum conditions and then move along the way of both increasing the gas phase pressure (to address the ?pressure gap' problem) and complicating the samples under study from single crystals to supported clusters (to address the ?material gap' problem). The case studies cited in the review prove the efficacy of the proposed approach to investigations into the reactivity of active component particles for the subsequent molecular design of catalysts with improved performance (activity, selectivity and stability) and demonstrate that it conforms with the modern trends in the development of surface science as applied to heterogeneous catalysis.
TRANSIENT RESPONSE STUDY OF THE FORMALDEHYDE OXIDATION TO FORMIC ACID ON V-Ti-O CATALYST: FTIR AND PULSE STUDY
G.Ya. Popova, T.V. Andrushkevich, Yu.A. Chesalov, V.N. Parmon
J. Mol. Catal., 268(1-2) (2007) pp. 251-256.
The mechanism of the formaldehyde oxidation to formic acid on a V-Ti-O catalyst has been studied by pulse and spectrokinetic (in situ FTIR) methods. Bidentate symmetrical formates and asymmetric formates are observed by formaldehyde adsorption both in the presence and in the absence of dioxygen in the temperature range between 100 and 200°C. Formic acid may form by two parallel pathways: by an associative mechanism through the oxidative elimination of bidentate formates and by a stepwise redox Mars – van Krevelen mechanism through the decomposition of asymmetric formates; the associative mechanism seems to be preferable.
INVESTIGATION OF THE REACTION MECHANISM OF METHYLPYRAZINE AMMOXIDATION ON VANADIA-TITANIA CATALYST BY FTIR IN SITU
V.M. Bondareva, T.V. Andrushkevich, E.A. Paukshtis, N.A. Paukshtis, A.A. Budneva, V.N. Parmon
J. Mol. Catal. A., 269(1-2) (2007) pp. 240-245.
The mechanism of methylpyrazine ammoxidation on a vanadia-titania catalyst has been studied by in situ FTIR spectroscopy. The structure of surface intermediates has been identified and the sequence of their transformation in the temperature range of 150-230°C has been ascertained. The interaction of methylpyrazine with catalyst surface includes a consecutive transformation of coordinatively bound methylpyrazine into oxygenated surface compounds, viz., an aldehyde-like complex and an asymmetrical carboxylate. The main reaction product, amidopyrazine, is formed through the interaction of the surface oxyintermediates with adsorbed ammonia species.
HIGH-TEMPERATURE CARBOXIDATION OF CYCLOPENTENE WITH NITROUS OXIDE
E.V. Starokon, K.S. Shubnikov, K.A. Dubkov, A.S. Kharitonov, G.I. Panov
Kinet. Catal., 48(3) (2007) pp. 376-380.
It is demonstrated by the example of cyclopentene that the noncatalytic oxidation of alkenes with nitrous oxide to carbonyl compounds (carboxidation), which is known to occur in the liquid phase at 150–250°C, can also take place in the gas phase at higher temperatures (300–475°C). Like liquid-phase carboxidation, the gas-phase reaction likely proceeds via a dipolar 1,3-addition mechanism. However, 4-pentenal is formed along with cyclopentanone in the gas phase. The 4-pentenal selectivity increases from 2.5 to 23% as the reaction temperature is raised. High-temperature cyclopentene carboxidation can be carried out in a paraffin melt (bp ~ 400°C). Filling the reactor with paraffin accelerates the reaction and reduces its activation energy.
LIQUID-PHASE NONCATALYTIC OXIDATION OF MONOTERPENOIDS WITH NITROUS OXIDE
E.P. Romanenko*, E.V. Starokon, G.I. Panov, A.V. Tkacheva* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. Chem. Bull., 56(6) (2007) pp. 1239-1243.
A series of monoterpenoids differing in the number of double bonds and the pattern of their substitution were tested in the liquid-phase noncatalytic oxidation with nitrous oxide (N2O). The structure of olefins has a significant effect on the oxidation route. In the case of terpenoids containing 1,1-disubstituted double bond, nor-carbonyl compounds are formed with high selectivity.
INVESTIGATION OF UNSTEADY-STATE REDOX MECHANISMS OVER CERIA BASED CATALYSTS FOR PARTIAL OXIDATION OF METHANE
C. Mirodatos*, Y. Schuurman*, A.C. van Veen*, V.A. Sadykov, L.G. Pinaeva, E.M. Sadovskaya (*Institut de Recherches sur la Catalyse, Villeurbanne Cedex, France)
Stud. Surf. Sci. Catal., 167 (2007) pp. 287-292.
The dynamics of transient experiments carried out on nanocrystalline CeO2-ZrO2 and Pt/CeO2-ZrO2 materials in POM appear to be associated with which might be determined by a high density of domain boundaries and Frenkel-type defects. T he profile of these transients is clearly related to the state of the catalyst (preoxidized or pre-reduced). The fast oxygen transfer from the support to Pt sites favors preferential routes for POM reactions over Pt clusters, although the mixed oxide alone displays a reasonably high activity. Domain boundaries might be involved also in storage of carbonates and hydroxyls which affects observed transients as well. All these mechanistic conclusions provide new trends for designing catalysts specifically adapted to applications involving essentially transient regimes.
CERIA-BASED FLUORITE-LIKE OXIDE SOLID SOLUTIONS PROMOTED BY PRECIOUS METALS AS CATALYSTS OF METHANE TRANSFORMATION INTO SYNGAS
V.A. Sadykov, T.G. Kuznetsova, G.M. Alikina, Yu.V. Frolova, A.I. Lukashevich, V.S. Muzykantov, V.A. Rogov, L.Ch. Batuev, V.V. Kriventsov, D.I. Kochubey, E.M. Moroz, D.A. Zyuzin, E.A. Paukshtis, E.B. Burgina, S.N. Trukhan, V.P. Ivanov, L.G. Pinaeva, Yu.A. Ivanova, V.G. Kostrovskii*, S. Neophytides**, E. Kemnitz***, K. Scheurel***, C. Mirodatos**** (*Institute of Solid-State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Institute of Chemical Engineering and High-Temperature Processes, Patras, Greece; ***Humboldt University, Berlin, Germany; ****Institut de Recherches sur la Catalyse CNRS, Villeurbanne, France)
In “New Topics in Catalysis Research”,Ed. D. McReynolds, 2006,Nova Science Publishers Inc., pp. 97-196.
For catalysts comprised of Pt supported onto dispersed complex fluorite-like oxides (ceria doped by Pr, Gd, Sm, or CeO2-ZrO2 doped by La, Gd or Pr), the effects of the oxygen mobility in supports and Pt dispersion on the performance in methane selective oxidation into syngas at short contact times were elucidated using combination of kinetic and spectroscopic methods. While in general any simple universal relation between the oxygen mobility, Pt dispersion and the rate of methane transformation into syngas was not found, for some series, a good correlation was observed agreeing with the bifunctional scheme of the methane selective oxidation into syngas.
METHANE OXIDATION OVER MIXED-CONDUCTING SrFe(Al)O3–δ–SrAl2O4 COMPOSITE
A.A. Yaremchenko*, V.V. Kharton*, A.A. Valente*, S.A. Veniaminov, V.D. Belyaev,V.A. Sobyanin, F.M.B. Marques* (*University of Aveiro, Aveiro, Portugal)
Phys. Chem. Chem. Phys., 9(21) (2007) pp. 2744-2752.
The steady-state CH4 conversion by oxygen permeating through mixed-conducting (SrFe)0.7(SrAl2) 0.3Oz composite membranes, comprising strontium-deficient SrFe(Al)O3–δperovskite and monoclinic SrAl2O4-based phases, occurs via different mechanisms in comparison to the dry methane interaction with the lattice oxygen. The catalytic behavior of powdered (SrFe)0.7(SrAl2)0.3Oz, studied by temperature-programmed reduction in dry CH4 at 523–1073 K, is governed by the level of oxygen nonstoichiometry in the crystal lattice of the perovskite component and is qualitatively similar to that of other perovskite-related ferrites, such as Sr0.7 La0.3Fe0.8Al0.2O3–δ. While extensive oxygen release from the ferrite lattice at 700–900 K leads to predominant total oxidation of methane, significant selectivity to synthesis gas formation, with H2/CO ratios close to 2, is observed above 1000 K, when a critical value of oxygen deficiency is achieved. The steady-state oxidation over dense membranes at 1123–1223 K results, however, in prevailing total combustion, particularly due to excessive oxygen chemical potential at the membrane surface. In combination with surface-limited oxygen permeability, mass transport limitations in a porous layer at the membrane permeate side prevent reduction and enable stable operation of (SrFe)0.7(SrAl2)0.3Oz membranes under air/methane gradient. Taking into account the catalytic activity of SrFeO3–δ-based phases for the partial oxidation of methane to synthesis gas and the important role of mass transport-related effects, one promising approach for membrane development is the fabrication of thick layer of porous ferrite-based c atalyst at the surface of dense (SrFe)0.7(SrAl2)0.3Oz composite.
METHANE OXIDATION BY LATTICE OXYGEN OF CeNbO4+δ
A.A. Yaremchenko*, V.V. Kharton*, S.A. Veniaminov, V.D. Belyaev, V.A. Sobyanin, F.M.B. Marques*(*University of Aveiro, Aveiro, Portugal)
Catal. Commun., 8(3) (2007) pp. 335-339.
The reactivity of methane with lattice oxygen of cerium niobate, CeNbO4+δ, was studied by temperature-programmed reduction (TPR) in dry CH4 flow at 523–1073 K. Phase transformations and reduction of cerium niobate at 900–1023 K lead to a massive release of hyperstoichiometric oxygen, in amounts determined by the intermediate-temperature phase composition dependent on thermal history. In this temperature range, CH4–TPR shows prevailing formation of carbon monoxide and steam, suggesting that the synthesis gas generation occurs in parallel with extensive oxidation of H2 on the cerium niobate surface. At 1073 K when δ → 0,, the reaction of methane with CeNbO4+δ selectively yields synthesis gas with H2/CO ratio close to two.
METHANE CARBONYLATION WITH CO ON SULFATED ZIRCONIA: EVIDENCE FROM SOLID-STATE NMR FOR THE SELECTIVE FORMATION OF ACETIC ACID
M.V. Luzgin, V.A. Rogov A.G. Stepanov, N.S. Kotsarenko, V.P. Shmachkova
J. Phys. Chem. C, 111(28) (2007) pp. 10624-10629.
Using 13C and 1H solid-state NMR it has been shown, that methane can be carbonylated with carbon monoxide to give acetic acid on solid acid catalyst, sulfated zirconia. The carbonylation occurs at 473-573 K with high selectivity and essential conversion. The reaction proceeds both in the absence and in the presence of molecular oxygen. In the presence of oxygen, the catalyst can be used for the carbonylation of further portion of methane without reactivation in air. The mechanism of the reaction is discussed. The reaction observed opens up new possibilities of using sulfated zirconia-based solid catalysts for the synthesis of acetic acid from methane and carbon monoxide.
LIQUID-PHASE OXIDATION OF α-PINENE WITH OXYGEN CATALYZED BY CARBONSUPPORTED PLATINUM METALS
L.I. Kuznetsova, N.I. Kuznetsova, A.S. Lisitsyn, I.E. Beck, V.A. Likholobov*, J.E. Ancel** (*Institute of Hydrocarbon Processing, Omsk, Russia; **ARCHEMIS, Decines Charpieu Cédex, France) Kinet. Catal., 48(1) (2007) pp. 38-44.The liquid-phase oxidation of α-pinene with oxygen at 70–90°C is studied in the presence of Pd, Pt, Ru, Rh, and Ir supported on carbon. The conversion of α-pinene and the selectivity of formation of the main reaction products, namely, verbenol (1), verbenone (2), and α-pinene oxide (3), depends on the nature of the metal, on its oxidation state and extent of dispersion, and on the admixtures introduced into the system. In the presence of the Pt catalysts and promoting admixtures of tetrahexylammonium chloride (Hex4NCl), the selectivity of formation of the most valuable oxidation products (1 + 2) reaches 50% at an α-pinene conversion of 20–30%. The fraction of resinlike oxidation products decreases in the presence of the catalysts. The results obtained are discussed in the framework of the radical mechanism of α-pinene oxidation.
CATALYTIC HYDRODECHLORINATION ON PALLADIUM-CONTAINING CATALYSTS
A.G. Gentsler, V.I. Simagina, O.V. Netskina, O.V. Komova, S.V. Tsybulya, O.G. AbrosimovKinet. Catal., 48(1) (2007) pp. 60-66.
The catalytic liquid-phase hydrodechlorination of chlorobenzene on supported palladium-containing catalysts has been investigated. The following processes capable of deactivating the catalyst occur during the liquid-phase hydrodechlorination: the coarsening of supported metal particles, the washoff of the active component with the reaction medium, and potassium chloride deposition on the catalyst surface. The effects of the active component composition and of the preparation method on the hydrodechlorination activity and deactivation stability of the catalysts have been studied. The catalysts have been characterized by several physical methods.
EXPERIMENTAL STUDY OF THE GAS-PHASE HYDROFLUORINATION OF PERCHLOROETHYLENE OVER A CHROMIUM-BASED CATALYST
A.A. Zirka, S.I. Reshetnikov
React. Kinet. Catal. Lett., 90(1) (2007) pp. 213-214.
Gas-phase hydrofluorination of perchloroethylene to pentafluoroethane in the presence of a chromium-magnesium catalyst at 0.4 MPa and 330-390°C has been studied. А reaction scheme taking into account the formation of by-products is suggested.
Ti- AND Zr-MONOSUBSTITUTED POLYOXOMETALATES AS MOLECULAR MODELS FOR STUDYING MECHANISMS OF OXIDATION CATALYSIS
O.A. Kholdeeva, R.I. Maksimovskaya
J. Mol. Catal. A: Chem., 262(1-2) (2007) pp. 7-24.
Recent developments in the application of titanium- and zirconium-monosubstituted Keggin-type polyoxometalates (Ti- and Zr-POMs) as molecular models for studying mechanisms of H2O2-based selective oxidation catalysis are reviewed. The similarity in the catalytic behavior of Ti- and Zr-POMs and heterogeneous Ti(IV) and Zr(IV) single-site selective oxidation catalysts is demonstrated. The progress on the synthesis of Ti- and Zr-POMs, studying their interaction with H2O and H2O2, and characterization of the peroxo species formed are surveyed, with special emphasis being placed on the role of protons in the activation of the peroxo species.
THE NATURE OF AUTOCATALYSIS IN THE BUTLEROV REACTION
A.N. Simonov, O.P. Pestunova, L.G. Matvienko, V.N. Parmon
Kinet. Catal., 48(2) (2007) pp. 245-254.
The effect of the nature of an initiator on the kinetics of formaldehyde consumption and on product composition in the Butlerov reaction was studied in a stirred flow reactor and a batch reactor. It was found that, under flow conditions, the kinetics and the product composition of this reaction are independent of the nature of the initiator. The reaction schemes proposed previously for an autocatalytic process mechanism based on the formation of glycolaldehyde from two formaldehyde molecules are incorrect. A correlation between the initiating activities of various monosaccharides and the rates of their conversion into an enediol form was found with the use of a batch reactor. Solid enediol complexes with Ca2+ ions were isolated for glucose, fructose, ribose, and sorbose; the initiating activity of these complexes was found to be much higher than the initiating activity of pure monosaccharides. A self-consistent mechanism was proposed for Butlerov reaction initiation. The formation of the enediol forms of monosaccharides followed by degradation to lower carbohydrates plays a key role in this mechanism. In turn, the initiating activity depends on the position of the carbonyl group in the monosaccharide molecule. The condensation reactions of glycolaldehyde, glyceraldehyde, and dihydroxyacetone with each other were studied. Based on data on the condensation products of lower carbohydrates, a scheme was proposed for the Butlerov reaction. According to this reaction scheme, C2 and C3 carbohydrates mainly undergo an aldol condensation reaction with formaldehyde, whereas the formation of higher monosaccharides occurs by the aldol condensation of lower C2–C3 carbohydrates with each other.
SYMMETRIC OXIDATION OF SULFIDES WITH H2O2 CATALYZED BY TITANIUM COMPLEX AMINOALCOHOL DERIVED SCHIFF BASES
K.P. Bryliakov, E.P. Talsi
J. Mol. Catal. A., 264(1-2) (2007) pp. 280-287.
Sulfoxidation catalysts generated in situ from titanium(IV) isopropoxide and enantiopure Schiff bases promote the enantioselective oxidation of alkyl aryl sulfides to the corresponding sulfoxides at low catalyst loadings (<1 mol%), 30% aqueous hydrogen peroxide being the terminal oxidant. Upon screening of several ligands derived from β-aminoalcohols and salicylaldehydes, a catalyst affording sulfoxides with over 90% chemoselectivity and up to 60% ee was found, and the kinetics of the catalytic reaction was analyzed by 1H NMR.
THE ACTIVE INTERMEDIATES OF NON-HEME-IRON-BASED SYSTEMS FOR CATALYTIC ALKENE EPOXIDATION WITH H2O2/CH3COOH
E.A. Duban, K.P. Bryliakov, E.P. Talsi
Eur. J. Inorg. Chem., 6 (2007) pp. 852-857.
N,N’-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2diaminoethane) and [FeII(TPA)(CH3CN)2](ClO4)2 (2) (TPA = tris(2-pyridylmethyl)amine) are rare examples of iron-based catalysts for selective olefin epoxidation with H2O2/CH3COOH combination. Using 1,2H NMR and EPR spectroscopy, it was shown that the active species of the catalytic systems 1/H2O2/СH3COOH and 2/H2O2/СH3COOH are mononuclear iron(IV)-oxo complexes [(BPMEN)FeIV=O(S)]2+ and [(TPA)FeIV=O(S)]2+, respectively (S = solvent molecule). These intermediates are formed via decomposition of the corresponding acylperoxo complexes [(L)FeIII(O3CCH3)]2+ (L = BPMEN or TPA). The acylperoxo complex [(BPMEN)FeIII(O3CCD3)]2+ was identified in the catalytic system 1/H2O2/СD3COOD by 2H NMR spectroscopy. The improved epoxidation activity and selectivity of the catalytic systems 1/H2O2/CH3COOH and 2/H2O2/CH3COOH, with respect to 1/H2O2 and 2/H2O2, is caused by the effective formation of intermediates [(L)FeIV=O(S)]2+ via decomposition of the acylperoxo complexes [(L)FeIII(O3CCH3)]2+.
IRON CATALYZED OXIDATION OF THIOETHERS BY IODOSYLARENES: STEREOSELECTIVITY AND REACTION MECHANISM
K.P. Bryliakov, E.P. Talsi
Chem. Eur. J., 13(28) (2007) pp. 8045-8050.
Catalytic properties of a series of iron(III)-salen (salen=N,N'-bis(salicylidene)ethylenediamine dianion) and related complexes in asymmetric sulfoxidation reactions, with iodosylarenes as terminal oxidants, have been explored. These catalysts have been found to efficiently catalyze oxidation of alkyl aryl sulfides to sulfoxides with high chemoselectivity (up to 100 %) and moderate-to-high enantioselectivity (up to 84 % with isopropylthiobenzene and iodosylmesitylene), the TON (TON=turnover number) approaching 500. The influence of the ligand (electronic and steric effects of the substituents), oxidant, and substrate structures on the oxidation stereoselectivity has been investigated systematically. The structure of the reactive intermediates (complexes of the type [FeIII(ArIO)(salen)] and the reaction mechanism have been revealed by both mechanistic studies with different iodosylarenes and direct in situ 1H NMR observation of the formation of the reactive species and its reaction with the substrate.
MECHANISM OF THE REACTION NO + H2 ON THE Pt(100)-HEX SURFACE UNDER CONDITIONS OF THE SPATIALLY NONUNIFORM DISTRIBUTION OF REACTING SPECIES
M.Yu. Smirnov, D.Yu. Zemlyanov*, E.I. Vovk (*Purdue University, Birck Nanotechnology Center, West Lafayette, USA)
Kinet. Catal., 48(6) (2007) pp. 853-863.
The interaction of hydrogen with NOads/1 1 islands produced by NO adsorption on the reconstructed surface Pt(100)-hex was studied by high-resolution electron energy loss spectroscopy (HREELS) and the temperature-programmed reaction (TPR) method. The islands are areas of the unreconstructed surface Pt(100)-1 × 1 saturated with NOads molecules. The hexagonal phase around these islands adsorbs much more hydrogen near room temperature than does the clean Pt(100)-hex surface. It is assumed that hydrogen is adsorbed on the hexagonal surface areas that are adjacent to, and are modified by, the NOads/1 × 1 islands. The reaction of adsorbed hydrogen atoms with NOads takes place upon heating and has the character of so-called surface explosion. The TPR peaks of the products of this reaction—nitrogen and water—occur at Tdes~ 365–370 K, their full width at half-maximum being ~5–10 K. In the case of the NOads/1 1 islands preactivated by heating in vacuo above the NO desorption onset temperature (375–425 K), after the admission of hydrogen at 300 K, the reaction proceeds in an autocatalytic regime and the product formation rate increases monotonically at its initial stage. In the case of activation at 375 K, during the initial, slow stage of the reaction (induction period), hydrogen reacts with nitric oxide molecules bound to structure defects (NOdef). After activation at 425 K, the induction period is characterized by the formation and consumption of imido species (NHads). It is assumed that NHads formation involves Nads atoms that have resulted from NOads dissociation on defects upon thermal activation. The induction period is followed by a rapid stage of the reaction, during which hydrogen reacts with NO1 1 molecules adsorbed on 1 1 areas, irrespective of the activation temperature. After the completion of the reaction, the areas of the unreconstructed phase 1 1 are saturated with adsorbed hydrogen. The formation of Hads is accompanied by the formation of a small amount of amino species (NH2ads).
REACTION OF CO OXIDATION ON PLATINUM, RHODIUM, A PLATINUM-RHODIUM ALLOY, AND A HETEROPHASE BIMETALLIC PLATINUM/RHODIUM SURFACE
A.V. Kalinkin, A.V. Pashis, V.I. Bukhtiyarov
Kinet. Catal., 48(2) (2007) pp. 298-304.
The reaction of CO oxidation on thin metal films of platinum, rhodium, and their alloy and on a heterophase bimetallic Pt/Rh surface that consisted of platinum particles of size 10–20 nm on the surface of rhodium was studied in the region of low reactant pressures (lower than 2 × 10–5 mbar). At low temperatures (T < 200°C), the activity of samples increased in the order Rh > Pt/Rh > Pt–Rh alloy > Pt. Above 200°C, the rate of reaction on the heterophase Pt/Rh surface was almost twice as high as the sum of the rates of reaction on the individual metals; this fact is indicative of a synergistic effect. The nature of this effect is considered.
THE MOLECULAR MECHANISM OF LOWTEMPERATURE DECOMPOSITION OF HYDROGEN SULFIDE UNDER CONJUGATED CHEMISORPTION-CATALYSIS CONDITIONS
I.I. Zakharov, A.N. Startsev, O.V. Voroshina, A.V. Pashigreva, N.A. Chashkova, V.N. Parmon
Russ. J. Phys. Chem. A, 80(9) (2006) pp. 1403-1410.
The molecular mechanism of interaction of two hydrogen sulfide molecules with the (CoIII-Ho)2S2(SH2)4 model active center containing occluded hydrogen was studied by the density functional theory method with the B3P86 hybrid exchangecorrelation functional. The reaction was found to occur in the following elementary steps: molecular adsorption of hydrogen sulfide dissociative chemisorption S-S bond formation in the surface intermediate {2CoIII − (μ-S2) + 2H(ads)} with the release of the first hydrogen molecule into the gas phase H2(g) the release of the second hydrogen molecule into the gas phase H2(g) the formation of cyclooctasulfur in the reaction 4S2(ads) → S8(ads). The first three steps occur spontaneously at room temperature, the thermodynamic driving force of the process being the stoichiometric reaction of S-S bond formation at the stage of conjugated chemisorption of two hydrogen sulfide molecules on two adjacent metal ions with the release of the first hydrogen molecule into the gas phase. The catalytic cycle is terminated by the recombination of molecular sulfur S2 into cyclooctasulfur S8 in the adsorption layer and the release of the second hydrogen molecule into the gas phase.
EFFECTS OF THE PROPERTIES OF SO4/ZrO2 SOLID CATALYSTS ON THE PRODUCTS OF TRANSFORMATION AND REACTION MECHANISM OF R-(+)-LIMONENE DIEPOXIDES
O.V. Salomatina*, T.G. Kuznetsova, D.V. Korchagina*, E.A. Paukshtis, E.M. Moroz, K.P. Volcho*, V.A. Barkhash*, N.F. Salakhutdinov* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
J. Mol. Catal. A: Chem., 269(1-2) (2007) pp. 72-80.
Transformations of limonene diepoxides on solid SO4/ZrO2 catalysts in dried methylene chloride at room temperature were investigated by varying the amounts of supported sulfate ions and zirconia polymorphs. A method for estimating acid centers from DRIFTS spectra of adsorbed pyridine on the solid catalyst in a dried methylene chloride solution has been developed. It is shown that the mechanism of diepoxide transformations is changed by varying the type and amount of acid centers. At a 0.9–3% level of sulfation, Lewis centers are mainly responsible for the initial cleavage of the 8,9-epoxy group of limonene diepoxides (route B). At higher contents of sulfate ions (up to 30 wt.% SO4), the key transformations proceed with cleavage of the 1,2-epoxy group (route A) and involve the Brønsted centers. The type of support affects the structural features of the sulfate ions, which govern the rearrangement of limonene diepoxides by route A or B. Transformation of limonene diepoxides on the Lewis centers formed on sulfated alumina follows mainly route A. The type of acid centers also affects the stereochemical composition of the product mixture.
VANADIUM SPECIES IN NEW CATALYSTS FOR THE SELECTIVE OXIDATION OF METHANE TO FORMALDEHYDE: ACTIVATION OF THE CATALYTIC SITES
H. Launay*, S. Loridant*, D.L. Nguyen*, A.M. Volodin, J.L. Dubois*, J.M.M. Millet** (*Institut de Recherches sur la Catalyse et l’Environnement de Lyon, Villeurbanne, France; **Arkema, Centre de Recherches Rhône-Alpes, Pierre-Bénite cedex, France)
Catal. Today, 128(3-4) (2007) pp. 176-182.
New vanadium oxide supported on mesoporous silica catalysts for the oxidation of methane to formaldehyde were investigated by infrared and Raman spectroscopies to identify and characterize the molecular structure of the most active and selective catalytic sites. In situ and operando experiments have been conducted in order to understand the redox and hydroxylation/dehydroxylation processes of the vanadium species. (SiO)2VO(OH) species were identified in these catalysts in reaction conditions and shown to undergo a deprotonation at 580°C under vacuum, leading to a site giving a photoluminescence band at 550 nm attributed to reverse radiative decay from the excited triplet state: V4+–O−) ↔ (V5+=O2−). An activation mechanism of vanadium monomeric species with electrophilic oxygen species is proposed.
STATE OF PALLADIUM IN PALLADIUM-ALUMINOSILICATE CATALYSTS AS STUDIED BY XPS AND THE CATALYTIC ACTIVITY OF THE CATALYSTS IN THE DEEP OXIDATION OF METHANE
P.G. Tsyrul’nikov*, T.N. Afonasenko*, S.V. Koscheev, A.I. Boronin (*Institute of Hydrocarbon Processing, Omsk, Russia)
Kinet. Catal., 48(5) (2007) pp. 728-734.
Palladium catalysts based on Siralox and AS aluminosilicate supports for the deep oxidation of methane were studied. With the use of XRD analysis, it was found that they were heterophase systems consisting of an amorphous aluminosilicate and γ-Al2O3 stabilized against agglomeration. It was found that the catalytic activity of palladiumaluminosilicate catalysts in the deep oxidation of methane at 500°C depended on the support precalcination temperature. X-ray photoelectron spectroscopy (XPS) was used to study the states of the AS-30 aluminosilicate support calcined at 600, 800, or 1000°C and palladium supported on it. It was found that the action of an acid impregnation solution of palladium nitrate on the aluminosilicate calcined at 800°C resulted in a structural rearrangement of the aluminosilicate surface. This rearrangement resulted in the stabilization of both palladium oxide and palladium metal particles at surface defects and the incorporation of these particles into the aluminosilicate after catalyst calcination. As a result, an anomalous decrease in catalytic activity was observed in aluminosilicate samples calcined at 800°C. According to XPS data, palladium in the catalyst was stabilized in the following three phases: metal (Eb(Pd3d5/2) = 334.8 eV), oxide (Eb(Pd3d5/2) = 336.8 eV), and “interaction” (Eb(Pd3d5/2) = 335.8 eV) phases. The ratio between these phases depended on support and catalyst calcination temperatures. The interaction phase, which consisted of PdOx clusters stabilized in the aluminosilicate structure, was responsible for the etention of activity after calcination at high temperatures (800°C). Based on an analysis of XPS data, it was hypothesized that palladium in the interaction phase occurred in a charged state with the formal charge on the Pd atom close to 1+ (δ+ phase).
ON THE INVOLVEMENT OF RADICAL OXYGEN SPECIES O– IN CATALYTIC OXIDATION OF BENZENE TO PHENOL BY NITROUS OXIDE
V.S. Chernyavsky, L.V. Piryutko, A.K. Uriarte*, A.S. Kharitonov, G.I. Panov (* Solutia Inc., Gonzales, FL, USA)
J. Catal., 245(2) (2007) 466-469.
Catalytic oxidation of benzene to phenol by nitrous oxide over Fe-MFI zeolites was studied in relation to the active oxygen species taking part in the oxidation. A linear dependence of the reaction rate on the concentration of independently identified active sites generating O– radicals (α-sites) has been obtained within a broad range of values. The dependence is interpreted as a convincing evidence of the O– involvement in the catalytic (not only stoichiometric) oxidation of benzene to phenol. This conclusion is of particular importance in connection with a long discussion in the literature on a possible role of O– radicals in selective oxidation catalysis over V and Mo oxides. Reliable evidence of the catalytic role of O– obtained with zeolites may renew a general interest in the once suggested but not recognized radical oxygen idea in the oxidation over widely used metal oxide catalysts.
ACTIVE SURFACE FORMATION ON A PROMOTED COPPER CATALYST OF THE PARTIAL OXIDATION OF ETHANOL
A.A. Magaeva*, V.S. Shmotin**, O.V. Vodyankina**, A.S. Knyazev**, A.N. Salanov, Yu.A. Chesalov, E.S. Stoyanov, G.V. Odegova, L.N. Kurina** (*Department of Structural Macrokinetics, Tomsk Scientific Center, Russia; **Tomsk State University, Tomsk, Russia)
Russ. J. Phys. Chem. A, 80(5) (2006) pp. 706-713.
The catalytic properties, chemical composition, and morphology of the surface of electrolytic copper crystals promoted with phosphorus as catalysts of the partial oxidation of ethanol into acetaldehyde were studied. A mechanism of active copper surface formation under the action of the promoting admixture was suggested. Promotion was shown to cause the formation of copper polyphosphates on the surface. Particles of copper metal responsible for selective alcohol transformation are formed in a promoter layer under the action of the reaction medium.
BIFUNCTIONAL CATALYSTS FOR HYDROGEN PRODUCTION FROM DIMETHYL ETHER
G.G. Volkova, S.D. Badmaev, V.D. Belyaev, L.M. Plyasova, A.A. Budneva, E.A. Paukshtis, V.I. Zaikovsky, V.A. Sobyanin
Stud. Sur. Sci. Catal., 167 (2007) pp. 445-450.
The production of hydrogen directly from dimethyl ether (DME) was performed on bifunctional Cu-Ce/Al2O3 catalysts. The catalysts were characterized by XRD, HRTEM, EDX and IR spectroscopy of low-temperature CO adsorption. The high hydrogen productivity up to 600 mmol g-1 h-1 may be explained by assuming that (1) DME dehydration occurs on acid sites of γ-Al2O3 and (2) methanol steam reforming takes place on mixed oxide phase CuO-CeO2, solid solution of copper ions in cerium dioxide with ratio Cu/Ce from 12/86 to 33/67 at.%.
ACTIVITY OF MoSe2/Al2O3 CATALYSTS IN DECOMPOSITION OF THIOPHENE AND SELENOPHENE
D.I. Kochubey, V.A. Rogov, V.P. Babenko
React. Kinet. Catal. Lett., 90(1) (2007) pp. 167-177.
The rate of thiophene decomposition was shown to be independent of the type of chalcogens used in catalysts MoX2/Al2O3, where X = S, Se. On the contrary, the rate of selenophene decomposition was shown to be higher on catalysts MoSe2 than that on MoS2. This observation suggests that the decomposition proceeds on anion vacancies. The decomposition of either thiophene over MoSe2 or selenophene over MoS2 results in the formation of partially substituted chalcogenides. At that, the molar ratios of the substituted chalcogen to Mo were shown to coincide in both cases. The fact that the rate of the thiophene decomposition does not depend on the degree of anion exchange indicates that the decomposition is not associated with hydrogenolysis.
STUDY OF METHANE DEHYDROAROMATIZATION ON IMPREGNATED Mo/ZSM-5 CATALYSTS AND CHARACTERIZATION OF NANOSTRUCTURED Mo PHASES AND CARBONACEOUS DEPOSITS
E.V. Matus, I.Z. Ismagilov, O.B. Sukhova, V.I. Zaikovskii, L.T. Tsykoza, Z.R. Ismagilov, J.A. Moulijn* (*Delft University of Technology, Delft, The Netherlands)
Ind. Eng. Chem. Res., 46(12) (2007) pp. 4063-4074.
Methane dehydroaromatization was studied over the series of impregnated Mo/ZSM-5 catalysts with different molybdenum contents and Si/Al atomic ratios in the parent H-ZSM-5 zeolites. The maximum catalytic activity (CH4 conversion ~ 14%) and benzene formation selectivity (~ 70%) were observed for the samples with 2-5% Mo. The activity and selectivity are improving when Si/Al is decreased from 45 to 17. After the pre-treatment in argon and reaction at 720°C, the catalysts have been characterized by textural methods, XRD, DTA, HRTEM and EDX. As determined by HRTEM, after the pre-treatment the MoOx phase is highly dispersed on the external surface of zeolite. During the reaction, Mo carbide nanoparticles of 2-15 nm in size are forming on the external surface, and the Mocontaining clusters - in the zeolite channels. The carbonaceous deposits (CD) are forming as the graphite layers on the surface of Mo2C nanoparticles larger than 2 nm, and as the friable layers with disordered structure - on the external surface of zeolite. According to EDX, XRD and DTA, the content of CD and extent of their condensation (C/H ratio) are increasing with time-on-stream. For the all studied Mo contents (1-10%) and time-onstream values (0.5-6 h), the CD formed on the catalysts with Si/Al = 17 are characterized by one maximum of the exothermic burn-out effect in DTA, whereas on the catalysts with Si/Al = 30 and 45 – by two such maxima. A correlation between the catalyst activity, selectivity vs. nanostructure and location of the Mo phases and CD is discussed.
Co-Pt BIMETALLIC CATALYSTS FOR THE SELECTIVE OXIDATION OF CARBON MONOXIDE IN HYDROGEN-CONTAINING MIXTURES
P.V. Snytnikov, K.V. Yusenko*, S.V. Korenev*, Yu.V. Shubin*, V.A. Sobyanin (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Kinet. Catal., 48(2) (2007) pp. 276-281.
The performance of a Co–Pt powder and of Co–Pt catalysts supported on ν-Al2O3 and on the graphitelike carbon material Sibunit in selective CO oxidation in hydrogen-containing mixtures is considered. Fine particles of metal–metal solid solutions and intermetallides were obtained by the decomposition of a Co- and Pt-containing double complex salt in a hydrogen atmosphere at ~400°C. As compared to their Pt and Co monometallic counterparts, the bimetallic catalysts are more active and allow the CO concentration in hydrogen-containing mixtures to be reduced from 1 to 10–3 vol %. This effect is likely due to the formation of bimetallic particles of a Co–Pt solid solution on the support surface.
COPPER-CERIUM OXIDE CATALYSTS FOR THE SELECTIVE OXIDATION OF CARBON MONOXIDE IN HYDROGEN-CONTAINING MIXTURES. I. CATALYTIC ACTIVITY
P.V. Snytnikov, A.I. Stadnichenko, G.L. Semin, V.D. Belyaev, A.I. Boronin, V.A. Sobyanin
Kinet. Catal., 48(3) (2007) pp. 439-447.
A series of copper–cerium oxide catalysts were prepared, and their properties toward the reaction of CO oxidation in hydrogen-containing gas mixtures were studied. It was found that the copper–cerium oxide catalysts are stable, active, and selective in this reaction. The conditions under which these catalysts decreased the concentration of CO from 1 to <10–3 vol % in hydrogen containing water vapor and carbon dioxide were determined.
COPPER-CERIUM OXIDE CATALYSTS FOR THE SELECTIVE OXIDATION OF CARBON MONOXIDE IN HYDROGEN-CONTAINING MIXTURES. II. PHYSICOCHEMICAL CHARACTERIZATION OF THE CATALYSTS
P.V. Snytnikov, A.I. Stadnichenko, G.L. Semin, V.D. Belyaev, A.I. Boronin, V.A. Sobyanin
Kinet. Catal., 48(3) (2007) pp. 448-456.
The copper–cerium oxide catalysts were characterized using a set of physicochemical techniques including in situ FTIR spectroscopy, XPS, and XRD. It was found that copper segregated on the surface of cerium oxide and its states were labile and dependent on catalyst pretreatment conditions. Copper in a dispersed state was responsible for the reaction of CO oxidation in the presence of H2 on the copper– cerium oxide catalysts. It is likely that this state of copper was composed of two-dimensional or threedimensional surface clusters containing Cu+ ions.
STEAM REFORMING OF DIMETHYL ETHER TO HYDROGEN-RICH GAS OVER BIFUNCTIONAL СuO-CeO2/γ-Al2O3-CATALYSTS
S.D. Badmaev, V.A. Sobyanin
Chem. Sustain. Devel., 15(1) (2007) pp. 117-121.
The steam reforming of dimethyl ether (DME) (SR) to a hydrogen-rich gas over a bifunctional СuO-CeO2/γ-Al2O3-catalysts, containing surface sites responsible for proceeding of the reactions of DME hydration and steam methanol conversion was studied. The catalysts were shown to possess high activity and selectivity in DME steam reforming. The hydrogen production rate in DME SR was found to reach 0,47-0,61 mol H2/(gcat·h) at 350°C, gas hourly space velocity of 10000 h−1 and molar ratio H2O/DME = 3. The vol.% of CO in the hydrogen-rich gas is lower than equilibrium value and not exceeding 1 %.
STEAM REFORMING OF DIMETHYL ETHER TO HYDROGEN-RICH GAS
S.D. Badmaev, G.G. Volkova, V.D. Belyaev, V.A. Sobyanin
React. Kinet. Catal. Lett., 90(1) (2007) pp. 205-211.
The steam reforming of dimethyl ether (DME) (SR) to a hydrogen-rich gas over a mechanical mixture of WOx/ZrO2 (the DME hydration catalyst) and CuZnAlOx (the methanol SR catalyst) was studied. The mechanically mixed catalyst was shown to provide almost complete conversion of DME to the hydrogen-rich gas containing <0.5 vol.% of CO at 300°C, atmospheric pressure, gas hourly space velocity (GHSV) of 10000 h−1 and molar ratio H2O/DME = 3. The hydrogen production rate in DME SR was found to reach 180–250 mmol H2/(gcat·h) at 250–300°C.
HYDRATION OF DIMETHYL ETHER TO METHANOL OVER SOLID ACIDS
S.D. Badmaev, V.D. Belyaev, G.G. Volkova, E.A. Paukshtis, V.A. Sobyanin
React. Kinet. Catal. Lett., 90(1) (2007) pp. 197-204.
The hydration of dimethyl ether (DME) to methanol over various solid acids was studied. The acidity of the catalysts is determined by FTIR spectroscopy. The hydration is found to occur predominantly on the Brönsted acid sites. Among the catalysts studied, WOx/ZrO2 and H-ZSM-5 appeared to be most active and selective.
ELUCIDATION OF THE NATURE OF ACTIVE OXYGEN IN THE REACTION OF LOW-TEMPERATURE OXIDATION OF CO ON SINGLE CRYSTAL SURFACES PLATINUM AND PALLADIUM
V.V. Gorodetskii, A.A. Sametova, A.V. Matveev, N.N. Bulgakov
Russ. J. Phys. Chem. B, 1(2) (2007) pp. 130-137.
The role of the surface reconstruction, subsurface oxygen (Оsubs) and concentration of СОads molecules was revealed in the low-temperature CO oxidation on Pt (100), Pt (410), Pd (111) and Pd (110) surfaces by HREELS, TPR and molecular beams methods. The possibility of the formation of so-called “hot” oxygen atoms, which arise at the surface at the instant of dissociation of O2ads molecules and can react with COads at low temperatures (~150 K) to form CO2, was examined. It was revealed that, when present in high concentration, COads initiates the phase transition of the Pt(100)-(hex) reconstructed surface into the (1×1) non-reconstructed one and blocks fourfold hollow sites of oxygen adsorption (Pt4-Oads), thereby initiating the formation of weakly bound oxygen (Pt2-Oads), highly-active in CO oxidation. For the Pt(410), Pd(111), and Pd(110) surfaces, the reactivity of Oads with respect to CO was demonstrated to be dependent on the surface coverage of COads. The 18Oads isotope label was used to determine the nature of active oxygen reacting with CO at ~150-200 K. It was examined why a COads layer produces a strong effect on the reactivity of atomic oxygen. The experimental results were confirmed by theoretical calculations based on the minimization of the Gibbs energy of the adsorption layer. According to these calculations, the COads layer causes a decrease in the apparent activation energy Eact of the reaction due to changes in the type of coordination and in the energy of binding of Oads atoms to the surface.EFFECT OF THE MODIFICATION OF ZrO2-CONTAINING PILLARED CLAY WITH Pt AND Cu ATOMS ON THE PROPERTIES OF INORGANIC COMPLEX INTERMEDIATES IN THE SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES WITH PROPYLENE ACCORDING TO IN SITU IR-SPECTROSCOPIC DATA
V.A. Matyshak*, V.F. Tret’yakov**, T.N. Burdeinaya**, K.A. Chernyshov*, V.A. Sadykov, O.N. Sil’chenkova*, V.N. Korchak* (*Semenov Institute of Chemical Physics, Moscow, Russia; **Topchiev Institute of Petrochemical Synthesis, Moscow, Russia)
Kinet. Catal., 48(1) (2007) pp. 74-83.
It was found that only bridging and bidentate nitrate complexes were formed on the surface of Pt,Cu/ZrO2-pillared interlayered clay (ZrO2PILC) upon the interaction with a flow of the (0.2% NO + 2.5% O2)/N2 mixture, whereas monodentate and nitrosyl complexes were not detected. The concentration of nitrate complexes on Pt,Cu/ZrO2-PILC was higher and the strength of their bond to the surface was weaker than those on unmodified ZrO2-PILC. Isopropoxide and acetate complexes and coordinatively bound acetone were formed on the surface in the interaction of Pt,Cu/ZrO2-PILC with a flow of the (0.2% C3H6 + 2.5% O2)/N2 mixture. The supporting of Pt and Cu onto zirconium dioxide pillars resulted in considerable changes in the concentration and the temperature region of the existence of hydrocarbon surface compounds, as compared with ZrO2-PILC. Under reaction conditions at relatively low temperatures, isopropoxide and nitrate intermediates on the surface of Pt,Cu/ZrO2-PILC formed a complex structurally similar to adsorbed dinitropropane. At elevated temperatures, a surface nitromethane complex was formed in the interaction of the acetate complex with nitrate species. The spectrokinetic measurements demonstrated that the apparent rate constants of consumption of nitrate and nitroorganic complexes considerably increased on going from ZrO2-PILC to Pt,Cu/ZrO2-PILC. Moreover, the constants of consumption of nitroorganic and nitrate complexes were similar for both of the catalysts. This fact suggests that, on the test catalysts, nitroorganic complexes were reaction intermediates in the selective catalytic reduction of NOxx (NOx SCR) with hydrocarbons. The found differences in the activation species and thermal stabilities of reactants can explain different activities of ZrO2-PILC and Pt,Cu/ZrO2-PILC in the SCR reaction of NOx with propylene in an excess of oxygen.
SPECIFICS OF THE DESORPTION OF OXYGEN FROM A SILVER SURFACE PROMOTED BY PHOSPHATES
N.V. Dorofeeva*, A.S. Knyazev**, N.I. Radishevskaya*, A.N. Salanov, L.P. Shilyaeva**, N.N. Sudakova**, O.V. Vodyankina** (*Polytechnical University, Tomsk, Russia; **Tomsk State University, Tomsk, Russia)
Russ. J. Phys. Chem. A, 81(5) (2007) pp. 788-793.
The interaction of oxygen with the surface of a polycrystalline silver catalyst promoted with phosphorus-containing compounds was studied by the temperature-programmed desorption method. It was demonstrated that the introduction of a phosphoruscontaining promoter gives rise to the formation of predominantly high-temperature forms of oxygen, which are more strongly bonded to the catalyst surface. The chemical composition of the active silver surface at various stages of its evolution was determined by IR spectroscopy. Under the action of temperature and a reducer, the polyphosphate promoter layer was observed to produce metal silver particles, which participate in the formation of active sites at the catalyst surface.
KINETICS OF OXYGEN EXCHANGE OVER CeO2ZrO2 FLUORITE-BASED CATALYSTS
E.M. Sadovskaya, Yu.A. Ivanova, L.G. Pinaeva, G. Grasso*, T.G. Kuznetsova, A. van Veen*, V.A. Sadykov, C. Mirodatos* (*Institut de Recherches sur la Catalyse, Villeurbanne Cedex, France)
J. Phys. Chem. A, 111(20) (2007) pp. 4498-4505.
The kinetics of 18O/16O isotopic exchange over CeO2-ZrO2-La2O3 and Pt/CeO2-ZrO2 catalysts have been investigated under the conditions of dynamic adsorption–desorption equilibrium at atmospheric pressure and temperature range 650-850°C. The rates of oxygen adsorption/desorption on Pt sites, support surface, oxygen transfer (spillover) from Pt to the support as well as the amount of oxygen accumulated in the oxide bulk and oxygen diffusion coefficient were estimated. The nanocrystalline structure of lanthana doped ceria-zirconia prepared via the Pechini route with a developed network of domain boundaries and specific defects guarantees a high oxygen mobility in the oxide bulk (D = (1.5÷2.0)·10-18 m2s-1 at 6500C) and allows accumulation of overstoichiometric/ excess oxygen. For Pt/CeO2-ZrO2 oxygen transfer from Pt to support (characteristic time < 10-2 s) was shown to be responsible for the fast exchange between the gas phase oxygen and oxygen adsorbed on the mixed oxide surface. The rate of direct exchange between the gas phase and surface oxygen is increased as well, due to the increased concentration (up to 2 monolayers) of surface/near subsurface oxygen species accumulated on the oxygen vacancies (originated from the incorporation of highly dispersed Pt atoms). The characteristic time of diffusion of the oxygen localized in the subsurface layers is about 1 s. The overall quantity of overstoichiometric oxygen and/or hydroxyl groups accumulated in the bulk can reach the equivalent of 10 monolayers, and characteristic time of oxygen diffusion within the bulk is about 20 s. All these kinetic data are required for the further step of modeling partial oxidation of hydrocarbons under steady- and unsteady-state conditions.
REGIOSELECTIVE H/D EXCHANGE OF PROPANE ON Zn/H-MFI ZEOLITE
A.G. Stepanov, S.S. Arzumanov, V.N. Parmon, Yu.G. Kolyagin*, I.I. Ivanova*, D. Freude** (*Moscow Lomonosov State University, Moscow Russia, **Abteilung Grenzflächen-Physik, Universität Leipzig, Leipzig, Germany)
Catal. Lett., 114(1-2) (2007) pp. 85-90.
The hydrogen exchange for propane-d8 adsorbed on zeolite Zn/H-MFI has been studied by 1H MAS NMR spectroscopy in situ within the temperature range of 420–490 K. Kinetic measurements of the H/D exchange between the acidic hydroxyl groups of the zeolite and the adsorbed deuterated propane molecules show that only methyl groups of the alkane are involved in the exchange. Two mechanisms are proposed to rationalize the regioselectivity of the exchange: (i) propane dehydrogenation on Zn-sites followed by protonation of propene by acidic OH groups in accordance to the Markovnikov’s rule and abstraction of deuteride ion from another propane molecule; (ii) the reversible heterolytic dissociative adsorption of propane to form Zn-propyl species and acidic OH groups.
DYNAMICS OF LINEAR n-C6 - n-C22 ALKANES INSIDE 5A ZEOLITE STUDIED BY 2H NMR
D.I. Kolokolov, S.S. Arzumanov, A.G. Stepanov, H. Jobic* (*Institut de Recherches sur la Catalyse, Villeurbanne Cedex, France)
J. Phys. Chem. C, 111(11) (2007) pp. 4393-4403.
The dynamic behavior of deuterated analogues of linear alkanes, n-C6 - n-C22, adsorbed in zeolite 5A has been studied by deuterium solid-state NMR (2H NMR). Temperature dependences of spin-lattice (T1) and spin-spin (T2) relaxation times of the deuterium located in the CD3 groups of the adsorbed n-alkanes were rationalized on the basis of a model derived for the motion of n-alkanes located in the pores of the zeolite. The model implies that the adsorbed molecules consist of two ensembles: diffusing (or stretched) and temporarily blocked from diffusion (or coiled). The possible intramolecular motions for the alkane chains were taken into account based on both the finite size of the zeolite cage and the allowable hydrocarbon chain conformations. The coiled molecules are involved in two modes of motion: isotropic reorientation and intramolecular conformational isomerization, whereas the stretched molecules are additionally involved in a diffusion process. Dynamics parameters for different modes of motion and a proportion of the blocked and stretched molecules were derived from the analysis of relaxation data. The estimated proportion of the diffusing molecules correlates with the alkanes diffusivities earlier obtained by neutron spin echo measurements.
KINETIC MODEL AND MECHANISM OF THE SELECTIVE OXIDATION OF CO IN THE PRESENCE OF HYDROGEN ON PLATINUM CATALYSTS
P.V. Snytnikov, V.D. Belyaev, V.A. Sobyanin
Kinet. Catal., 48(1) (2007) pp. 93-102.
The reaction kinetics of the selective oxidation of carbon monoxide in the presence of hydrogen on a Pt/carbon support catalyst was studied. It was found that this catalyst exhibited high activity and decreased the concentration of CO in a hydrogen-containing gas from 0.6–1.0 vol % to less than 10 ppm at the inlet concentration ratio O2/CO = 1.0–1.5. A kinetic model of the reaction was proposed to describe quantitatively the experimental results.IN SITU NMR SPECTROSCOPY IN HETEROGENEOUS CATALYSIS: KINETIC STUDY OF HYDROCARBON CONVERSION MECHANISMS
A.G. Stepanov, V.N. Parmon, D. Freude* (*University of Leipzig, Leipzig, Germany)
Kinet. Catal., 48(4) (2007) pp. 521-534.
The potential of high-resolution solid-state NMR spectroscopy for kinetic and mechanistic studies of hydrocarbon conversion on solid acid catalysts between 20 and 300°C is considered. The use of this technique is illustrated by the elucidation of the mechanisms of hydrogen exchange and 13C label transfer in alkanes and olefins, n-butane isomerization on sulfated zirconia, and ethane aromatization on zinccontaining zeolite beta. The kinetic parameters determined in these studies provide a basis for quantum chemical calculations of possible hydrocarbon activation and conversion pathways and for evaluating the reliability and accuracy of these theoretical calculations.
HOMOGENEOUS HIGH-TEMPERATURE OXIDATION OF METHANE
A.A. Slepterev*, V.S. Salnikov*, P.G. Tsyrulnikov*, A.S. Noskov, V.N. Tomilov, N.A. Chumakova, A.N. Zagoruiko (*Institute of Hydrocarbon Processing, Omsk, Russia)
React. Kinet. Catal. Lett., 91(2) (2007) pp. 273-282.
The kinetics of homogeneous deep oxidation of methane in lean mixtures (up to 2 vol % CH4 in air) in ceramic tubes and fixed beds of ceramic spheres was studied. Experiments with the homogeneous reaction have shown that the methane oxidation occurs via a consecutive scheme through CO formation. The reaction rate of CH4 oxidation was found to depend upon the equivalent pass diameter with a significant reaction inhibition in packing of small tubes and spheres, reflecting the influence of mass transfer on the radical-chain termination at the ceramic surfaces. It was also found that CO oxidation practically does not depend upon the mass exchange conditions, but it is visibly inhibited by methane. Recommended kinetic equations and their parameters are presented.
KINETICS OF ALUMINUM POWDER OXIDATION BY WATER AT 100°C
S.F. Tikhov, V.A. Sadykov, A.I. Ratko*, T.F. Kuznetsova*, V.E. Romanenkov*, S.I. Eremenko* (*Institute of General and Inorganic Chemistry, Minsk, Belarus)
React. Kinet. Catal. Lett., 92(1) (2007) pp. 83-88.
The kinetics of aluminum powder oxidation by water at 100°С has been investigated using three types of aluminum powders. A “shrinking sphere” model was used for the description of experimental data at the initial reaction stage, whereas a diffusion “parabolic” equation was used at the second stage. Variation of the specific reactivity is discussed.
AROMATIZATION OF LIGHT NAPHTA FRACTION ON ZEOLITES. 3. MODEL OF COKE FORMATION
N.M. Ostrovski*, S.A. Rovenskaja**, G.V. Echevsky (*Chemical Industry HIPOL, Odžaci, Serbia; **Omsk State University, Omsk, Russia)
CI&CEQ, 13(2) (2007) pp. 51-54.
Previously the authors reported on the reaction kinetic and catalyst deactivation models for the Zeoforming process. The significant coking takes place, and two types of coke are formed. In this work the equations of coke accumulation are derived and its relations with relative activities are presented and discussed.
NONOXIDATIVE METHANE CONVERSION INTO AROMATIC HYDROCARBONS ON TUNGSTEN-CONTAINING PENTASILS
A.V. Vosmerikov*, G.V. Echevsky, L.L. Korobitsyna*, N.V. Arbuzova*, E.G. Kodenev, L.M. Velichkina*, C.P. Zhuravkov** (*Institute of Petroleum Chemistry, Tomsk, Russia; **Institute of Strength Physics and Materials Science, Tomsk, Russia)
Kinet. Catal., 48(3) (2007) pp. 409-413.
The effects of the tungsten concentration and of the method of tungsten introduction into ZSM-5 pentasils with different SiO2/Al2O3molar ratios on the acidity and the activity of the resulting catalysts in non-oxidative methane conversion into aromatic hydrocarbons are considered. The catalysts obtained from the SiO2/Al2O3 = 40 pentasil and a nanosized tungsten powder are the most active and the most stable. The maximum methane conversion and the highest yield of aromatic hydrocarbons are achieved on the zeolite containing 8.0 wt % tungsten nanopowder.
ZrFe INTERMETALLIDES FOR FISCHER-TROPSCH SYNTHESIS: PURE AND ENCAPSULATED INTO ALUMINACONTAINING MATRICES
S.F. Tikhov, A.E. Kuzmin*, Yu.N. Bespalko, V.I. Kurkin*, V.A. Sadykov, E.I. Bogolepova*, S.V. Tsybulya, A.V. Kalinkin, V.P. Mordovin, A.N. Salanov, V.I. Zaikovskii, A.A. Shavorsky (*Topchiev Institute of Petrochemical Synthesis, Moscow, Russia)
Stud. Surf. Sci. Catal., 163 (2007) pp. 153-175.
Performance of the bulk hydrogenated ZrFe intermetallides both pure and encapsulated into alumina-containing matrix (Al2O3/Al, Al2O3) was studied in catalysis of Fischer-Tropsch synthesis. Their structural, textural and surface properties were characterized by combination of such methods as XRD, SEM, TEM, nitrogen adsorption-desorption isotherms and XPS, and impact of these properties on catalytic activity and selectivity was analyzed. The highest activity per the surface Fe atom (~5.10-19 CHx/at.Fe.h) was obtained for pure active component, while the highest activity per the unit of volume (~168 g C5+/l.h) was revealed for a composite catalyst at 300°C, 3 MPa and space velocity ~7000 h-1.
THE USE OF RDF ANALYSIS IN THE STUDY OF POWDER SAMPLES: ZIRCONIA COMPLEX SUPPORTED BY CLAY AND PSEUDOBOEHMITE
E.M. Moroz, D.A. Zyuzin
Z. Kristallogr. Suppl., 26 (2007) pp. 273-278.
Two examples illustrating the use of radial distribution functions of electronic density to determine the structure of supported zirconia complex and particularities of the pseudoboehmite structure are reported.
RDF METHOD APPLICATION TO PHASE ANALYSIS OF X-RAY AMORPHOUS PRODUCTS OF GIBBSITE THERMAL ACTIVATION
K.I. Shefer, E.M. Moroz, L.I. Isupova, I.V. Kharina, Yu.Yu. Tanashev
Z. Kristallogr., suppl_26 (2007) pp. 279-282.
The phase compositions of finely dispersed initial and rehydrated products of gibbsite thermal activation prepared by different technological methods – thermochemical activation (TCA) and centrifugal thermal activation (CTA) were studied using radial distribution function (RDF) method. The initial phase composition was shown to depend on the preparation method and determine the composition of the rehydrated products. Nuclei of different hydroxide phases are formed in addition to χ-alumina – pseudoboehmite in the case of the TCA process and bayerite for the CTA process. This leads to different phase compositions of rehydrated products. For TCA, pseudoboehmite is the primary rehydration product, whereas bayerite is formed for CTA.
METHOD FOR CONSTRUCTING THE RADIAL DISTRIBUTION CURVES
E.M. Moroz, D.A. Zyuzin, K.I. Shefer
J. Struct. Chem., 48(2) (2007) pp. 262-266.
A method for constructing the model radial distribution curves of electron density is described. The utility of this technique for the refinement of structure and phase composition for highly disperse materials is demonstrated by reference to several examples.
RADIAL DISTRIBUTION MODEL CURVES OF ELECTRON DENSITY FOR ALUMINUM OXIDES AND HYDROXIDES
E.M. Moroz, D.A. Zyuzin, K.I. Shefer, L.A. Isupova
J. Struct. Chem., 48(4) (2007) pp. 704-707.
Radial distribution model curves of electron density were constructed for various aluminum oxides and hydroxides that can be used for the refinement of the phase composition and structural features of these highly disperse materials employed as catalyst supports.
SUPPORTED MODIFIED MANGANESE-PALLADIUM CATALYSTS OF MPK-1 TYPE FOR CO OXIDATION REACTION
V.Sh. Bakhtadze*, N.D. Kharabadze*, E.M. Moroz (*Agladze Institute of Inorganic Chemistry and Electrochemistry, Tbilisi, Georgia)
Catal. Ind., 3 (2007) pp. 3-9.
The process of formation of active Mn-oxide phase in dependence of its concentration and type of carriers: SHN (γ-, χ-Al2O3) and SHN-2M (κ-Al2O3, CaO*2Al2O33) using X-ray phase and thermal analyses was studied. Optimal catalyst: 4-5 Mn, 0,05 Pd(mass%)/SHN-2М corresponds by composition to pilot sample of catalyst MPK-1. Calcination in air at 900°C, 10 h leads to decrease of the mechanical solidity of the sample MPK-1/SHN-2 from 7,5 to 3,2 MPa and decrease of its specific surface area from 98,0 to 10,0 m2/g. However, for the sample MPK-1/SHN-2M calcination results in decrease of its specific surface area to 50,0 m2/g, but the mechanical solidity of this catalyst does not change. This treatment leads to increase of temperature of reaching the 75 % degree of CO conversion at 130°C and 50°C for catalysts MPK-1/SHN-2 and MPK-1/SHN-2M, respectively. For both carriers formation of solid solution of Mn4+ was observed. Catalysts were examined in the systems of cleaning of exhaust gases of automotive engines and recommended for further practical use.
VACANCIES ORDERING IN La3+1-xBa2+xFeO3-δ PEROVSKITES
A.N. Nadeev, S.V. Tsybulya, G.N. Kryukova*, I.S. Yakovleva, L.A. Isupova (*GNF e. V., Berlin-Adlershof, Berlin, Germany)
Z. Kristallogr., suppl_26 (2007) pp. 381-386.
Using powder X-ray diffraction the La3+ 1-xBa2+xFeO3-δ perovskite related solid solutions were investigated. A morphotropic phase transition from orthorhombic to cubic was shown for the sample with x ~ 0.3. High temperature XRD patterns of La0.2Ba0.8FeO3-δ obtained under air and vacuum revealed new diffraction peaks related to local ordering of the oxygen vacancies. Such ordering remained at room temperature only after cooling in vacuum.
HIGH-TEMPERATURE STUDIES OF La1− xSrxFeO3−δ SOLID SOLUTIONS USING SYNCHROTRON RADIATION
A.N. Nadeev, S.V. Tsybulya, A.N. Shmakov, G.N. Kryukova*, I.S. Yakovleva, L.A. Isupova (*GNF e.V., Berlin-Adlershof, Germany)
J. Struct. Chem., 48(6) (2007) pp. 1105-1109.
A series of La1−x SrxFeO3−δ samples with a
perovskite structure were investigated by hightemperature
X-ray analysis using synchrotron
radiation. In this series, one can observe a
morphotropic phase transition (0.3≤x≤0.4) from the
orthorhombic (0≤x<0.3) to cubic (0.4 CHARACTERIZATION OF NEW CATALYSTS
BASED ON URANIUM OXIDES Z.R. Ismagilov, S.V. Kuntsevich, V.V. Kuznetsov,
N.V. Shikina, M.A. Kerzhentsev, V.A. Rogov,
V.A. Ushakov Kinet. Catal., 48(4) (2007) pp. 511-520. Catalysts based on uranium oxides were
systematically studied for the first time. Catalysts
containing various amounts of uranium oxides (5 and
15%) supported on alumina and mixed Ni–U/Al2O3
catalysts were synthesized. The uranium oxide
catalysts were characterized using the thermal
desorption of argon, the low-temperature adsorption
of nitrogen, X-ray diffraction analysis, and
temperature-programmed reduction with hydrogen
and CO. The effects of composition, preparation
conditions, and thermal treatment on physicochemical
properties and catalytic activity in the
reactions of methane and butane oxidation, the steam
and carbon dioxide reforming of methane, and the
partial oxidation of methane were studied. It was
found that a catalyst containing 5% U on alumina
calcined at 1000°C was most active in the reaction of
high-temperature methane oxidation. For the
Ni–U/Al2O3 catalysts containing various uranium
amounts (from 0 to 30%), the introduction of uranium
as a catalyst constituent considerably increased the
catalytic activity in methane steam reforming and
partial oxidation. STRUCTURAL STUDY OF HIGHLY
DISPERSED CERIUM DIOXIDES V.P. Kolko, E.M. Moroz, V.V. Kriventsov,
D.A. Zyuzin Bull. Russ. Acad. Sci.: Phys.,
71(5) (2007) pp. 695-698. Cerium dioxide samples of different dispersivity,
obtained by different methods, have been investigated
by X-ray diffraction (XRD) analysis, full-profile
analysis of diffraction patterns, calculation of radial
distribution function (RDF) of electron density, and
extended X-ray absorption fine-structure (EXAFS)
spectroscopy. According to the XRD data, the samples
studied can be identified in the fluorite structure with
conventional unit-cell parameters. However, the local
structure of highly dispersed samples, determined by
the RDF and EXAFS methods, changes: the
coordination spheres for the Ce–O distances are
represented by two distances. STRUCTURAL DETERMINATION OF
CERIA–ZIRCONIA NANOSYSTEM
DOPED BY Gd V.P. Kolko, V.V. Kriventsov, D.I. Kochubey,
D.A. Zyuzin, E.M. Moroz, V.A. Sadykov,
G.R. Kosmambetova*, P.Y. Strizhak*
(*Pisarzhevskii Institute of Physical Chemistry, Kiev,
Ukraine) Nucl. Instrum. Methods Phys. Res., Sect. A,
575(1-2) (2007) pp. 91-95. The work is devoted to the structural study of
doped Gd ceria–zirconia nanosystem by the EXAFS,
WAXS (wide angle X-ray scattering) and XRD
methods. A polymerized complex precursor method
(Pechini route) was used for synthesis of ceria–
zirconia doped by Gd. It was found by XRD analysis
that samples of ceria–zirconia doped by Gd have a
CeO2-reference structure (a cubic fluorite-like
structure). However, analysis of the EXAFS and
WAXS revealed the existence of two solid solutions
with different content of zirconium cations, this
implies heterogeneity on local level of structure. STRUCTURE OF THE MIXED OXIDES
Mex(Ce0.5Zr0.5)1 –xOy (Me = Gd, Pd) V.P. Kolko, D.A. Zyuzin, V.A. Sadykov,
V.V. Kriventsov, E.M. Moroz Glass Phys. Chem.,
33(4) (2007) pp. 335–339. The structure of the mixed oxides
Mex(Ce0.5Zr0.5)1 –xOy(x = 0, 0.1–0.30; y < 2) doped
with trivalent Gd and Pr metals is investigated using
the X-ray powder diffraction analysis, the full-profile
analysis of the diffraction pattern, and EXAFS
spectroscopy. The mixed oxides are solid solutions
with a structure similar to the CeO2 structure. An
increase in the content of the introduced trivalent
metal brings about an increase in the unit cell
parameter and a disordering of the structure of the
oxides under investigation. STRUCTURE STABILIZING EFFECT OF
TUNGSTEN IN MIXED MOLYBDENUM OXIDE
WITH Mo5O14-TYPE STRUCTURE E. Rödel**, O. Timpe**, A. Trunschke**,
G.A. Zenkovets, G.N. Kryukova*, R. Schlögl**,
T. Ressler** (*GNF e.V., Berlin-Adlershof, Germany;
**Fritz-Haber-Institut der MPG, Berlin, Germany) Catal. Today, 126(1) (2007) pp. 112-118. Bulk structural properties of single phase
crystalline (Mo0.91V0.09)5O14 and (Mo0.68V0.23W0.09)5O14
materials were investigated using in situ X-ray
diffraction and in situ X-ray absorption spectroscopy
at three metal edges. Temperature programmed
experiments in reducing (propene) and oxidizing
(oxygen) atmosphere and isothermal redox
experiments at 773 K revealed differences in the bulk
properties of the two phases studied. A structure
stabilizing effect of tungsten in (MoVW)5O14 under
oxidizing conditions was found. Moreover, tungsten
centers in a (MoVW) oxide material exert a structuredirecting
effect towards re-oxidation to a Mo5O14-type
structure. XAS STUDY ON MICROSTRUCTURE OF Au
NANOPARTICLES DEPOSITED ON ALUMINA S.B. Erenburg*, B.L. Moroz, N.V. Bausk*,
V.I. Bukhtiyarov, S. Nikitenko** (*Nikolaev
Institute of Inorganic Chemistry, Novosibirsk, Russia;
**KU Leuven, DUBBLE-CRG & ESRF, Grenoble,
France) Nucl. Instrum. Methods Phys. Res., Sect. A,
575(1-2) (2007) pp. 105-108. X-ray adsorption spectroscopy (XAS) was applied
to the characterization of the Au/δ-Al2O3 catalysts
with different mean Au particle sizes
(dl = 2-28 nm) prepared via adsorption of anionic
Au(III) hydroxide complexes and calcined in air at
673 K. The parameters of local atomic surrounding for
Au atoms in these catalysts were determined using
XANES and EXAFS techniques at 12 and 296 K. In
all samples, the only phase detected was metallic gold.
A contraction of interatomic Au-Au distance (R1) and
a gradual decrease in the coordination number for the
first coordination shell of Au atoms (N1), as well as an
increase in the Debye-Waller factor (σ) were observed
with decreasing mean Au particle size. XPS AND TEM STUDIES ON THE ROLE OF
THE SUPPORT AND ALKALI PROMOTER IN
Ru/MgO AND Ru-Cs+/MgO CATALYSTS FOR
AMMONIA SYNTHESIS Yu.I. Larichev, B.L. Moroz, V.I. Zaikovskii,
S.M. Yunusov*, E.S. Kalyuzhnaya*, V.B. Shur*,
V.I. Bukhtiyarov (*Nesmeyanov Institute of
Organoelement Compounds, Moscow, Russia) J. Phys. Chem. C, 111(26) (2007) pp. 9426-9437. The chemical state of ruthenium in the Ru/MgO
and Ru−Cs+/MgO catalysts prepared by the incipient
wetness technique with the use of Ru(OH)Cl3 and
Cs2CO3 as the catalyst and promoter precursors,
respectively, is characterized by X-ray photoelectron
spectroscopy (XPS). The influence of the final state
effects (the differential charging and variations of the
relaxation energy) on the binding energy of Ru 3d5/2
core level measured for supported Ru nanoparticles is
estimated by comparison of the Fermi levels and the
modified Auger parameters determined for the
Ru/MgO and Ru−Cs+/MgO catalysts with the
corresponding characteristics of polycrystalline Ru
foil. High-resolution transmission electron microscopy
(HRTEM) in combination with energy dispersive
X-ray (EDX) microanalysis reveals that Ru particles
in the Ru−Cs+/MgO catalyst are covered with an
amorphous layer containing cesium. XPS data show
that the layer subjected to the prolonged treatment
with H2 at 450°C consists of cesium suboxide Сs2+хO.
The shift of the Ru 3d5/2 binding energy toward lower
values is found for the Ru−Cs+/MgO catalyst
(279.7 eV) with respect to metallic Ru (280.2 eV) and
the Ru/MgO catalyst (280.5 eV). It is assumed that the
shift results from a decrease in the work function of
ruthenium under the action of Cs+ cations located on
the Ru surface. The data obtained are used to explain
the sharp difference in the activities of the Ru/MgO
and Ru−Cs+/MgO catalysts for ammonia synthesis at
250–400°C. X-RAY PHOTOELECTRON SPECTROSCOPIC
STUDY OF THE INTERACTION OF
SUPPORTED METAL CATALYSTS WITH NOX M.Yu. Smirnov, A.V. Kalinkin, V.I. Bukhtiyarov J. Struct. Chem.,
48(6) (2007) pp. 1053-1060. The reactions of the platinum and rhodium model
catalysts applied to aluminum oxide with NOx
(10 Torr NO + 10 Torr O2) were studied by X-ray
photoelectron spectroscopy. The reaction conducted at
room temperature formed on the surface of the oxide
support the NO3,s − nitrate ions characterized by the
N1s line at 407.4 eV and O1s line at 533.1 eV and the
NO2,s
− nitrite ions characterized by the N1s line with a
binding energy of 404.7 eV. At the same time, the Pt4f
and Rh3d lines of the supported platinum particles are
shifted toward higher binding energies by 0.5–1.0 eV
and 0.7–1.2 eV, respectively. It is assumed that the
binding energies increase due to changes in the
chemical state of the platinum metal in which oxygen
is dissolved. The reaction of NOx with Pt/Al2O3 at
200°C forms platinum oxide defined by the Pt4f 7/2
line with a binding energy of 72.3 eV. MIXED LAYERED Ni–Mn–Co HYDROXIDES:
CRYSTAL STRUCTURE, ELECTRONIC STATE
OF IONS, AND THERMAL DECOMPOSITION N.V. Kosova*, E.T. Devyatkina*, V.V. Kaichev
(*Institute of Solid State Chemistry and
Mechanochemistry, Novosibirsk, Russia) J. Power Sources,
174(2) (2007) pp. 735-740. It has been shown that varying conditions of coprecipitation
processes, two types of mixed
Ni–Mn–Co hydroxides: either brucite, or hydrotalcitelike
(LDHs) - with different Ni/Mn/Co ratio can be
prepared. According to XPS study, these hydroxides
are mixed-valence materials: Ni ions present in
2+ oxidation state, whereas Mn and Co ions are in
3+/4+ and 2+/3+ state, respectively; their oxidation state
increases with an increase of their content in
hydroxides. For Ni-rich hydroxides, a strong effect of
nickel segregation is observed indicating that
chemistry of the surface and of the bulk is different.
Mixed Ni–Mn–Co hydroxides decompose in two steps
resulting in formation of NiO bunsenite and
(Ni,Co,Mn)3O4 spinel. OPTIMIZATION OF Ni2+/Ni3+ RATIO IN
LAYERED Li(Ni,Mn,Co)O2 CATHODES FOR
BETTER ELECTROCHEMISTRY N.V. Kosova*, E.T. Devyatkina*, V.V. Kaichev
(*Institute of Solid State Chemistry and
Mechanochemistry, Novosibirsk, Russia) J. Power Sources,
174(2) (2007) pp. 965-969. A study of the LiNi1−x−yCoxMnyO2 (x = y = 0.1;
0.2; 0.33) cathode materials prepared from mixed
hydroxides and LiOH using the method of mechanical
activation has been performed. All as prepared
materials were indexed in the R-3m space group. The
cell volume and the degree of structural disordering
decrease with reducing of Ni content. According to
XPS study, the main electronic state of d-ions in the
surface layer of particles corresponds to Ni2+, Co3+ and
Mn4+. However, the Ni2p3/2 and Co2p3/2 binding
energy increases versus Ni content, indicating the
increased Me-bond covalency. The highest specific
discharge capacity was observed for
LiNi0.6Co0.2Mn0.2O2 - 170 mAh g−1. The position of
redox peaks on the differential capacity curves
depends on the composition of the sample: it shifts
towards lower voltage with increased Ni content. LiNi1-x-yCoxMnyO2 (x = y = 0.1, 0.2, 0.33)
CATHODE MATERIALS PREPARED USING
MECHANICAL ACTIVATION: STRUCTURE,
STATE OF IONS, AND ELECTROCHEMICAL
PERFORMANCE N.V. Kosova*, E.T. Devyatkina*, V.V. Kaichev
(*Institute of Solid-State Chemistry and
Mechanochemistry, Novosibirsk, Russia) Inorg. Mater.,
43(2) (2007) pp. 185-193. LiNi1–x–yCoxMnyO2 (x = y = 0.1, 0.2, 0.33) cathode
materials synthesized from mechanically activated
mixtures of lithium hydroxide and nickel cobalt
manganese hydroxide were investigated. The materials
have a layered structure (sp. gr. R-3m). Their unit-cell
volume and the degree of disordering in their structure
decrease with decreasing nickel content. According to
XPS data, the major states of the transition-metal ions in
the surface layer of the materials are Ni2+, Co3+, and
Mn4+. With increasing nickel content, the Ni 2p3/2 and Co
2p3/2 binding energies increase, attesting to changes in
M–O bond covalence. The highest specific
electrochemical capacity, ~170 mA h/g, is offered by
LiNi0.6Co0.2Mn0.2O2. The position of redox peaks in the
differential capacity curves of the three materials depends
on composition: with increasing nickel content, the peaks
shift to lower voltages. XAFS AND NEUTRON DIFFRACTION STUDY
OF La1-xSrxCo1-yNbyO3 V.V. Efimov*, E. Efimova*, D. Karpinsky**,
D.I. Kochubey, V.V. Kriventsov, A. Kuzmin***,
S. Molodtsov****, V. Sikolenko*,*****,
J. Purans******, S. Tiutiunnikov*,
I.O. Troyanchuk**, A.N. Shmakov,
D. Vyalikh****** (*Joint Institute for Nuclear
Research, Dubna, Russia; **Institute of Solid State
and Semiconductor Physics, Minsk, Belarus;
***Institute of Solid State Physics, Riga, Latvia;
****Institut für Kristallographie und
Festkörperphysik, Dresden, Germany;
*****Hahn-Meitner-Institut, Berlin Germany;
******Dipartimento di Fisica, Universita’di Trento,
Trento, Italy) Nucl. Instrum. Methods Phys. Res., Sect. A,
575(1-2) (2007) pp. 176-179. The effect of hole doping on the crystal and
electronic structure of La1-xSrxCo1-yNbyO3
(y = 0.0-0.25) at the x = 0.0; 0.2; 0.5 has been studied
by neutron diffraction and X-ray absorption
spectroscopy at the Co K and L2,3-edges. The
preliminary analysis of the Co K and L2,3-edges
X-ray absorption near edge structure (XANES) in
La1-xSrxCo1-yNbyO3 series suggests that upon niobium
doping, an increase of the intermediate Co3+ spin state
and a decrease of low spin Co4+ states contributions
occur. The possible explanation of the observed
changes of crystal and electronic structure in these
cobaltites is discussed. XAFS AND NEUTRON DIFFRACTION STUDY
OF La1-xSrxCo1-yO3 V.V. Efimov*, E. Efimova*, D. Karpinsky**,
D.I. Kochubey, V.V. Kriventsov, A. Kuzmin***,
S. Molodtsov****, V. Sikolenko*,*****,
S. Tiutiunnikov*, I.O. Troyanchuk**,
A.N. Shmakov, D. Vyalikh****** (*Joint Institute
for Nuclear Research, Dubna, Moscow Region,
Russia; **Institute of Solid State and Semiconductor
Physics, Minsk, Belarus; ***Institute of Solid State
Physics, Riga, Latvia; ****Institut für
Kristallographie und Festkörperphysik, Dresden,
Germany; *****Hahn-Meitner-Institut, Berlin
Germany; ******Universita’di Trento, Trento, Italy) Phys. Status Solidi C, 4(3) (2007) pp. 805-808. The effects of hole doping on the crystal and
electronic structure of the La1-xSrxCo1-yO3 (x = 0.0÷0.5)
by neutron Rietveld analysis and its correlation with
the X-ray-absorption spectroscopy data have been
studied. The abrupt decrease of the Co-O distance and
an increase of the Co-O-Co angle upon substitution of
La3+ by Sr2+ in La1-xSrxCo1-yO3 are attributed to a change
in the band structure at the transition from
semiconducting to metallic state. Upon strontium
doping, a variation of Co L2,3-edges in La1-xSrxCo1-yO3
series suggests an increase of the mixed low Co4+ and
high or intermediate Co3+ spin states. The possible
explanation of the observed changes of the crystal and
electronic structure in these cobaltites is discussed. NEUTRON DIFFRACTION AND
SYNCHROTRON RADIATION STUDIES OF
La1-xSrxCoO3 MAGNETIC PROPERTIES V. Sikolenko*,**, A. Sazonov***,*****,
V. Efimov**, V.V. Kriventsov, N. Darowski*,
D. Vyalikh**** (*Hahn-Meitner-Institute, Berlin,
Germany; **Joint Institute for Nuclear Research,
Dubna, Russia; ***Joint Institute of Solid State and
Semiconductor Physics, Minsk, Belarus;
****Technical University of Dresden, Germany;
*****Institute of Crystallography, Aaahen, Germany) J. Magn. Magn. Mater.,
310(2) (2007) pp. e181-e183. Magnetic properties of the La1-xSrxCoO3solid
solutions have been studied by neutron diffraction and
X-ray absorption near edge structure (XANES)
measurements. Our data are in agreement with the
following scenarios. The first scenario is about the
magnetic phase separation into regions with different
content of Co3+/Co4+ ions in different spin states. The
second one is about the gradual thermal excitation of
the Co3+ ions from low- to intermediate- or high-spin
state in wide temperature range. PLUTONIUM AND NEPTUNIUM SPECIATION
BOUND TO HYDROUS FERRIC OXIDE
COLLOIDS S.N. Kalmykov*, V.V. Kriventsov, Y.A. Teterin**,
A.P. Novikov*** (*Lomonosov Moscow State
University, Moscow, Russia; **RNC “Kurchatov
Institute”, Moscow, Russia; ***Vernadsky Institute of
Geochemistry and Analytical Chemistry, Moscow
Russia) Comptes Rend. Chem.,
10(10-11) (2007) pp. 1060-1066. The speciation of plutonium and neptunium in
colloid suspension collected from the contaminated
aquifer of the “Mayak” site was studied by nano-
SIMS, XPS and XANES. At tracer level concentration
found in original groundwater sample Pu is sorbed
onto hydrous ferric oxide colloids, while at higher
concentration relevant to near-field conditions it forms
intrinsic PuO2 × nH2O colloids. The formation of such
colloids occurs through the reduction of Pu(V) to
Pu(IV) upon its sorption. SPECTROSCOPY OF HOMOGENEOUS
DEUTERATED HYDROCARBON FILMS
REDEPOSITED FROM T-10 TOPKAMAK
PLASMA DISCHARGE N.Yu. Svechnikov*, V.G. Stankevich*,
A.M. Lebedev*, K.A. Men’shikov*,
B.N. Kolbasov*, V.V. Kriventsov (*Russian
Research Center Kurchatov Institute, Moscow,
Russia) J. Surf. Invest. X-Ray,
Synchrotron and Neutron Techn.,
1 (2007) pp. 17-22. Homogeneous deuterated hydrocarbon films
redeposited from a deuterium plasma discharge inside
the T-10 tokamak vacuum chamber are studied using
photoluminescence methods; EXAFS, EPR, and IR
spectroscopies; and temperature measurements. The
photoluminescence excitation spectra of sp3-sp2
nanostructures of tokamak films are compared with
those of sp2 nanostructures of C60 fullerite films. The
effect of defect states on photoluminescence and its
temperature quenching is discussed. It is concluded
that the model of temperature luminescence quenching
for homogeneous deuterated tokamak films is similar
to that for amorphous a-C:H films. XAFS STUDY OF HIGH-DISPERSE
Pd-CONTAINING NANOSYSTEM SUPPORTED
ON TiO2 OXIDE MATRIX V.V. Kriventsov, B.N. Novgorodov,
D.I. Kochubey, O.V. Bukhtenko*,
M.V. Tsodikov*, N.Yu. Kozitsyna**,
M.N. Vargaftik**, I.I. Moiseev**, G. Colon***,
M.C. Hidalgo***, J.A. Navio***,
S.G. Nikitenko**** (*Topchiev Institute of
Petrochemical Synthesis, Moscow, Russia;
**Kurnakov Institute of General and Inorganic
Chemistry, Moscow, Russia; ***Instituto de Ciencia
de Materiales, Centro Mixto CSIC-Universidad,
Sevilla, Spain; ****KU Leuven, DUBBLE-CRG &
ESRF, Grenoble, France) Nucl. Instrum. Methods Phys. Res. A,
575(1-2) (2007) pp. 180-184. Recently, great efforts are devoted to develop new
methods of preparation of high-disperse Pd-containing
nanosystems (composed of metal and/or oxide
substance) stabilized on oxide matrix. New approach
of synthesis is usage of PdCo(μ-OOCMe)4(NCMe)
complex and Ti(OBu)4 as precursors to anchor Pd on
the surface of oxide matrix surface in a highly
dispersed form. The present work is devoted to the
structural study of this high-disperse Pd-containing
nanosystem by the XAFS spectroscopy. The strong
interaction between Pd and Co cations takes place in
the studied system. Seemingly, Co cations incorporate
into TiO2 oxide matrix, forming mixed oxides. This
allows to anchor Pd cations, with the formation of the
palladium oxide structures, modified by interaction
with Co and Ti cations. These compounds are
non-stochiometric and have typical structural features
of mixed oxides. All possible structural models are
discussed in detail. FEATURES OF LOCAL ATOMIC STRUCTURE
OF NANOCRYSTALLINE DISORDERED Fe–M
(M=Ge, Sn, Al, Si) ALLOYS: EXAFS-STUDY E. Voronina*, T. Miyanaga**, A. Deyev*,
V.V. Kriventsov, G. Konygin*, E. Yelsukov*
(*Physical-Technical Institute, Izhevsk, Russia;
**Hirosaki University, Hirosaki, Japan) Nucl. Instrum. Methods Phys. Res. A,
575(1-2) (2007) pp. 189-192. The EXAFS-study (Fe, Sn and Ge K-edges) of
disordered by mechanical activation binary
supersaturated nanocrystalline solid solutions Fe–Al,
Fe–Ge, Fe–Sn and Fe–Si is presented. The EXAFSspectra
are processed by solving the inverse binary
problem, using the EXAFS-spectrum of the
Fe K-edge only or combining the EXAFS-spectra on
two K-edges, Fe and Ge or Fe and Sn. The parameters
of partial correlation functions indicate chemical
short-range ordering, high local static distortions in
the lattice, increasing with metalloid content. The
macrostructure of other type is forming through an
initial, “local” stage within the bcc lattice. X-RAY EMISSION AND X-RAY
PHOTOELECTRON SPECTROSCOPIC
STUDIES OF FULLERENE FLUORIDE C60F24 Yu.V. Lavskaya*, A.V. Okotrub*,
L.G. Bulusheva*, E.M. Pazhetnov, A.I. Boronin,
N.I. Denisenko**, O.V. Boltalina*** (*Nikolaev
Institute of Inorganic Chemistry, Novosibirsk, Russia;
**Moscow Lomonosov State University, Moscow,
Russia; ***Colorado State University, Fort Collins,
USA) Phys. Solid State, 49(5) (2007) pp. 1195-1200. The structure of the fullerence fluoride C60F24 of
the Th symmetry contains two types of chemically
different carbon atoms, namely, atoms of isolated
double bonds and atoms of CF groups. X-ray
photoelectron and X-ray emission spectroscopic
studies of C60F24 revealed a difference in the widths of
the X-ray bands corresponding to these types of
atoms. Nonempirical quantum-chemical calculations
performed for C59NF24
+ ions with a hole in the C 1s
core level of the fullerence fluoride showed that the
difference in the bandwidths may be due to the fact
that the vibrational states of the system are different
when 1s electrons are removed from chemically
nonequivalent atoms. XPS STUDIES OF THE OXYGEN STATE
DURING OXIDATION OF
POLYCRYSTALLINE GOLD SURFACE A.I. Stadnichenko, S.V. Koscheev, A.I. Boronin Herald of the Moscow State University,
ser. 2, Chem.,
48(6) (2007) pp. 418-426. X-ray photoelectron spectroscopy (XPS) was used
to study oxide films on bulk gold obtained by highfrequency
activation of O2. It was established that this
method is effective for the formation of oxide films
thicker than 3–5 nm. Inspection of the Au4f spectra
revealed that the gold atoms are in 3+ state during the
surface oxidation. The complex structure of XPS
spectra of oxygen comprise 4 individual features that
characterize various non-equivalent states of oxygen
in the obtained oxide films. Presumably, two main
oxygen states (Еb(O1s) = 529.0 eV and 530.0 eV)
relate to oxygen atoms in the composition of two- and
three-dimensional gold oxide Au2O3. Oxygen species
with high bonding energies (Еb(O1s) = 531.8 eV and
535.2 eV) are most likely to be characterized by the
molecular oxygen state in the composition of peroxide
and superoxide groups, respectively. TEMPERATURE EFFECTS ON THE IR
SPECTRA OF CRYSTALLINE AMINO ACIDS,
DIPEPTIDES, AND POLYAMINO ACIDS.
I. GLYCINE G.B. Chernobai*,**, Yu.A. Chesalov, E.B. Burgina,
T.N. Drebushchak*,**, E.V. Boldyreva*,**
(*Novosibirsk State University, Novosibirsk, Russia;
**Institute of Solid State Chemistry and
Mechanochemistry, Novosibirsk, Russia) J. Struct. Chem.,
48(2) (2007) pp. 332-339. The IR spectra of the α, β, and γ polymorphic
modifications of pure glycine (without diluents) have
been studied in the temperature range 93–433 K;
changes in the IR spectra caused by variations of
temperature are correlated with previously obtained
diffraction data about polymorphic transitions,
anisotropic compression of structure, and changes in
hydrogen bond parameters. X-RAY CRYSTAL STRUCTURE OF
[BPMEN(Cl)FeIIIOFeIII(Cl)BPMEN](ClO4)2,
[BPMEN = N,N'-DIMETHYL-N,N'-BIS
(2-PYRIDYLMETHYL)ETHANE-1,2-DIAMINE]
AND THE ASSIGNMENT OF ITS 1H NMR
PEAKS IN CD3CN E.A. Duban, T.N. Drebushchak*, K.P. Bryliakov,
E.P. Talsi (*Institute of Solid State Chemistry and
Mechanochemistry, Novosibirsk, Russia) Mendeleev Commun.,
17(5) (2007) pp. 291-293. The complex [BPMEN(Cl)FeIIIOFeIII(Cl)BPMEN](ClO4)2, [BPMEN = N,N'-dimethyl-N,N'-bis
(2-pyridylmethyl)ethane-1,2-diamine] was prepared
and characterised by X-ray crystallography; the
1H NMR peaks of this complex in CD3CN were
assigned based on the integration and proximity of
particular protons to a paramagnetic centre. EPR IDENTIFICATION OF Zr(III)
COMPLEXES FORMED UPON INTERACTION
OF (2-PhInd)2ZrCl2 AND rac-Me2Si(1-Ind)2ZrCl2
WITH MAO AND MMAO O.Y. Lyakin, K.P. Bryliakov, V.N. Panchenko,
N.V. Semikolenova, V.A. Zakharov, E.P. Talsi Macromol. Chem. Phys.,208 (2007) pp. 1168-1175. Reactions of 1 and 2 with
MAO and MMAO were monitored by EPR. It was
found that MMAO is a stronger reducing agent than
MAO. 1 is more prone to reduction than 2. The
reduction of ZrIV to ZrIII seems to be the essential
pathway of some zirconocene catalysts' deactivation.
ZrIII species with the following proposed structures
can be identified in the 1/MMAO system:
(2-PhInd)2ZrIII(iBu), (2-PhInd)2ZrIII(μ-Cl)2AliBu2,
(2-PhInd)2ZrIII(μ-Cl)(iBu)AliBu2, and
[(2-PhInd)2ZrIII]+[Me-MAO]-. The degree of reduction
of ZrIV species determined by EPR in the catalytic
system 2/MMAO can be masked by the formation of
diamagnetic ZrIII/ZrIII dimers. Addition of monomers
to the 2/MAO system promotes reduction of the
zirconium species. 1H AND 13C NMR STUDIES OF CATIONIC
INTERMEDIATES FORMED UPON ACTIVATION OF “OSCILLATING”
CATALYSTS (2-PhInd)2ZrCl2 WITH MAO,
MMAO, AND AlMe3/[CPh3]+[B (C6F5)4] O.Y. Lyakin, K.P. Bryliakov, N.V. Semikolenova,
A.Y. Lebedev*, A.Z. Voskoboynikov*,
V.A. Zakharov, E.P. Talsi (*Moscow Lomonosov
State University, Moscow, Russia) Organomet.,
26(6) (2007) pp. 1536-1540. The conformationally dynamic unbridged
metallocene (2-PhInd)2ZrCl2 (1-Cl) was activated with
methylaluminoxane (MAO), modified
methylaluminoxane (MMAO), and
AlMe3/[CPh3]+[B(C6F5)4]-. The following ion pairs
were characterized by1 H and 13C NMR:
[(2-PhInd)2Zr(μ-Me)2AlMe2]+[Me-MAO]- (III),
[(2-PhInd)2Zr(μ-Me)2AlMe2]+[B(C6F5)4]- (III'),
[(2-PhInd)2Zr(μ-Me)2AlMeiBu]+[Me-MAO]-
(IIIMeiBu), [(2-PhInd)2Zr(μ-Me)2AliBu2]+[Me-MAO]-
(IIIiBuiBu), and [(2-PhInd)2ZrMe+···Me-MAO-] (IV). In
the temperature range -50 to 20°C, the rotation of
indenyl ligands of complexes III, III', and IIIMeiBu is
faster than the evaluated rate of propylene insertion,
whereas for IIIiBuiBu the rate of indenyl ligand rotation
is comparable to or slower than the rate of propylene
insertion. The ion pair IIIiBuiBu demonstrates the
fundamental possibility of the existence of
intermediates with the "locked" conformation of 2-
PhInd ligands in 1-Cl/MAO or
1-Cl/MMAO systems. For the catalytic system
1-Cl/MAO, both outer sphere ion pair III and inner
sphere ion pair IV are present in the reaction solution
at high [Al]MAO/[Zr] ratios. For the catalytic system
1-Cl/MMAO, the concentration of inner sphere ion
pairs of type IV is much smaller (below the NMR
detection limit), and only outer sphere ion pairs
IIIMeiBu and IIIiBuiBu are observed. 129Xe NMR STUDY OF THE LOCALIZATION
OF PdCl2 SUPPORTED ON CARBON
NANOTUBES K.V. Romanenko, P.A. Simonov, O.G. Abrosimov,
O.B. Lapina, A. Fonseca*, J.B. Nagy*,
J.-B. d’Espinose**, J. Fraissard** (*Laboratoire de
Resonance Magnetique Nucleaire, FUNDP, Namur,
Belgium; **Ecole Supérieure de Physique et de
Chimie Industrielles, Paris, France) React. Kinet. Catal. Lett.,
90(2) (2007) pp. 355-364. Localization of PdCl2 clusters supported on multiwall
carbon nanotubes (MWCNT) has been
investigated using 129Xe NMR of adsorbed xenon.
As-made MWCNTs with channels initially
inaccessible for adsorption and ball-milled MWCNTs
with the totally accessible internal surface were used
as supports. The observed 129Xe NMR spectra were
determined by the dynamics of xenon exchange
between the aggregate pores and nanotube channels.
No considerable changes of the 129Xe NMR spectrum
with the concentration of supported PdCl2 were
observed for the as-made MWCNT, while an
additional resonance appeared for the ball-milled
nanotubes. The 129Xe NMR experiments evidenced the
supported species to be localized on the internal
surface of the ball-milled MWCNT.
IS 129Xe NMR A USEFUL TECHNIQUE FOR
PROBING THE PORE STRUCTURE AND
SURFACE PROPERTIES OF CARBONACEOUS
SOLIDS? K.V. Romanenko, J.-B. d’Espinose de Lacaillerie*,
O.B. Lapina, J. Fraissard* (*Laboratoire de
Physique Quantique, ESPCI, Vauquelin, Paris,
France) Micropor. Mesopor. Mater.,
105 (2007) pp. 118-123. Generally the interpretation of 129Xe NMR data
obtained for porous carbons is complicated. There are
several reasons: structural disorder, distribution of the
crystallite size or presence of amorphous domains,
heterogeneity of surface properties, strong
paramagnetic sites, etc. Thus it would appear that
structural disorder, bad reproducibility of properties
and various impurities make 129Xe NMR ineffective
when applied to porous carbon materials. This
problem is re-examined for a series of microporous
carbons with similar surface chemical properties and
mesoporous carbons with a wide range of pore
diameters. In both cases there is no relationship
between the value, δS, of the chemical shift
extrapolated to zero concentration and the pore
diameter. However, the virial coefficient, δXe–Xe,
arising from binary xenon collisions in the free
volume, varies linearly with the micropore size. In the
case of mesoporous carbons there is a monotonic
decrease of this coefficient with the increase of the
pore size, if one take into account binary xenon
collisions at the pore surface. MULTINUCLEAR MAGNETIC RESONANCE
IMAGING AS A MULTIFUNCTIONAL TOOL
FOR THE INVESTIGATION OF THE
PROPERTIES OF MATERIALS, TRANSPORT
PROCESSES AND CATALYTIC REACTIONS I.V. Koptyug*, A.A. Lysova, K.V. Kovtunov*,
V.V. Zhivonitko*, A.V. Khomichev*,
R.Z. Sagdeev* (*International Tomography Center,
Novosibirsk, Russia) Russ. Chem. Rev.,
76(6) (2007) pp. 583-598. New physicochemical applications of
multinuclear magnetic resonance imaging that will
determine the development of the method in the near
future are considered. These include studies of solids,
investigations of mass transfer processes in multiphase
systems, studies on in situ reactors, heterogeneous
hydrogenation with para-hydrogen and spectroscopy
of long-lived singlet states. It is noted that in addition
to an extension of the range of objects and processes
of interest, the magnetic resonance imaging technique
itself undergoes considerable changes. MULTINUCLEAR MAGNETIC RESONANCE
IMAGING IN CATALYTIC RESEARCH:
RECENT ADVANCES AND FUTURE
PROSPECTS I.V. Koptyug*, A.A. Lysova, V.N. Parmon,
R.Z. Sagdeev* (*International Tomography Center,
Novosibirsk, Russia) Kinet. Catal., 48(4) (2007) pp. 464-468. The most important applications of magnetic
resonance imaging in catalysis and related areas are
considered. In combination with other advanced
instrumental methods, this technique can provide
essential information about the properties of catalysts
and reactors and about processes occurring there. The
examples given in the report include the preparation
and characterization of porous supports; loading of
supports with an active component by impregnation;
and investigation of the structure of a granular catalyst
bed, various mass transfer processes, and the
operation dynamics of a model reactor.
118 APPLICATION OF MULTINUCLEAR
MRI AND SOLID STATE MRI IN
HETEROGENEOUS CATALYSIS I.V. Koptyug*, A.A. Lysova, R.Z. Sagdeev*,
V.N. Parmon (*International Tomography Center,
Novosibirsk, Russia) Catal. Today,
126(1-2) (2007) pp. 37-43. This paper presents some of the existing
applications of the NMR imaging (MRI) technique
relevant to catalytic research. Through the examples
presented, it is demonstrated that MRI is a powerful
addition to other modern techniques employed to
characterize properties of catalysts and catalytic
reactors and their performance. It is shown that the
existing MRI approaches can be applied to get insight
into a broad range of characteristics of catalysts and
reactors. The examples presented include preparation
and characterization of porous catalyst supports,
dynamic studies of supported catalysts preparation by
solution impregnation, packing and structure of
catalyst beds and reactors, and various types of mass
transport in the catalyst particles as well as in the
entire reactor. Last but not least, it is shown that rapid
MRI strategies are useful to study dynamic processes
in operating catalytic reactors, with the multiphase
catalytic hydrogenation reaction at elevated
temperatures used as a representative example. These
in situ studies demonstrate a number of essential
phenomena including ignition of individual catalyst
particles and their mutual influence, while
combination of the spectroscopic and imaging
modalities of the NMR technique can be useful for the
characterization of the chemical conversion under
reactive conditions. 27Al NMR/MRI STUDIES OF THE TRANSPORT
OF GRANULAR Al2O3 I.V. Koptyug*, A.A. Lysova, A.V. Khomichev*,
R.Z. Sagdeev* (*International Tomography Center,
Novosibirsk, Russia) Diffusion Fundam.,
5 (2007) pp. 2.1-2.7 The NMR/MRI techniques are applicable to the
studies of motion of granular solids, providing
information on the velocities, effective diffusivities
and correlation times of the moving particles. The
studies of transport of granular solids reported to-date
are based on the detection of the 1H NMR signal of the
liquid phase of liquid-containing solid materials. Yet,
the solid phase of many granular solids contains
magnetic nuclei, providing in principle an opportunity
to study motion of such solids by directly detecting
the NMR signal of the solid phase. In this paper, it is
demonstrated that this can be performed with the use
of conventional echo pulse sequences in combination
with the conventional motion encoding schemes. The
detection of the 27Al NMR signal of the Al2O3 powder
was used to obtain velocity maps of the powder
packed in a spinning cylinder, and to measure the
velocity distribution (average propagator) for the
gravity driven transport of the same powder in a
vertical pipe. NUCLEAR MAGNETIC RESONANCE
IMAGING OF AN OPERATING
GAS–LIQUID–SOLID CATALYTIC
FIXED BED REACTOR A.A. Lysova, I.V. Koptyug*, A.V. Kulikov,
V.A. Kirillov, R.Z. Sagdeev*, V.N. Parmon
(*International Tomography Center, Novosibirsk,
Russia) Chem. Eng. J., 130(2-3) (2007) pp. 101-109. This work reports pioneering application of the
nuclear magnetic resonance imaging (MRI) technique
to the dynamic in situ studies of gas–liquid–solid
reactions carried out in a catalytic trickle bed reactor
at elevated temperature. The major advance of these
studies is that MRI experiments are performed under
reactive conditions. MRI have been applied to map the
distribution of liquid phase inside a catalyst pellet as
well as in a catalyst bed in an operating trickle-bed
reactor. In particular, the studies have revealed the
existence of the oscillating regimes of the
heterogeneous catalytic hydrogenation reaction caused
by the oscillations of the catalyst temperature and
directly demonstrated the existence of the coupling of
mass and heat transport and phase transitions with
chemical reaction. The existence of the partially
wetted pellets in a catalyst bed which are potentially
responsible for the appearance of hot spots in the
reactor has been also visualized. The combination of
NMR spectroscopy with MRI has been used to
visualize the spatial distribution of the reactant-toproduct
conversion within an operating reactor. 95Mo AND 17O NMR STUDIES OF AQUEOUS
MOLYBDATE SOLUTIONS R.I. Maksimovskaya, G.M. Maksimov Inorg. Chem.,
46(9) (2007) pp. 3688-3695. Aqueous molybdate solutions with molybdenum
concentrations of [Mo] = 1, 0.4, and
0.2 M have been studied by NMR at pH 7-1 and in
0.3-6 M HClO4. The 95Mo NMR spectrum of
isopolyanion (IPA) Mo7O24
6- (I) at pH = 5 consists of
a signal at 210 ppm and two overlapping peaks at
32 and ~15 ppm with the intensity ratio ~1:4:2, and
that of β-Mo8O26
4- (II) consists of two signals at ~100
and 10 ppm with the intensity ratio ~1:3. A broad
95Mo NMR line at around 0 ppm was observed in the
pH range of IPA Mo36O112
8- (III), and a signal of
cationic oxospecies including MoO2
2+ (IV) was
observed from -62 to -69 ppm. Two protonation sites
of IPA I have been identified from 17O NMR spectra,
which suggests binding of up to two protons. The
distribution diagram, derived from the 95Mo NMR
spectra, is given for [Mo] = 0.4 M. The 95Mo NMR
signals shift to lower frequencies with increasing
number and strength of the Mo-O terminal bonds. SOLID STATE NMR CHARACTERIZATION
OF INDIVIDUAL COMPOUNDS AND SOLID
SOLUTIONS FORMED IN
Sc2O3–V2O5–Nb2O5–Ta2O5 SYSTEM
D.F. Khabibulin, K.V. Romanenko, M. Zuev*,
O.B. Lapina (*Institute of Solid State Chemistry,
Ekaterinburg, Russia) Magn. Reson. Chem.,
45(11) (2007) pp. 962-970. In this study, 51V, 45Sc and 93Nb MAS NMR
combined with satellite transition spectroscopy
analysis were used to characterize the complex solid
mixtures: VNb9(1-x)Ta9xO25, ScNb(1-x)TaxO4 and
ScNb2(1-x)Ta2xVO9 (x = 0, 0.3, 0.5, 0.7, 1.0). This led to
describe the structures of Sc and V sites.
The conclusions were based on accurate values for 51V
quadrupole coupling and chemical shift tensors
obtained with 51V MAS NMR/SATRAS for VNb9O25,
VTa9O25 and ScVO4. The 45Sc NMR parameters have
been obtained for Sc2O3, ScVO4, ScNbO4 and ScTaO4.
On the basis of 45Sc NMR and data available from
literature, the ranges of the 45Sc chemical shift have
been established for ScO6 and ScO8. The gradual
change of the 45Sc and 51V NMR parameters with x
confirms the formation of solid solutions in the
process of synthesis of VNb9(1-x)Ta9xO25 and
ScNb(1-x)TaxO4, in contrast to ScNb2(1-x)Ta2xVO9. The
cation sublattice of ScNb(1-x)TaxO4 is found to be in
octahedral coordination. The V sites in
VNb9(1-x)Ta9xO25 are present in the form of slightly
distorted tetrahedra. The 93Nb NMR parameters have
been obtained for VNb9O25. INVESTIGATION OF THE FORMATION
PROCESS OF NANOSIZED PARTICLES
OF Ru(III) S.Yu. Troitskii, M.A. Fedotov, D.I. Kochubey,
B.N. Novgorodov, A.L. Chuvilin, V.A. Likholobov*
(*Institute for Hydrocarbons Processing, Omsk,
Russia) J. Struct. Chem.,
48(1) (2007) pp. 144-149. 17O, 35Cl, 133Cs NMR spectroscopy, static
magnetic susceptibility measurements, EXAFS,
UV spectroscopy, pH measurements, and electron
microscopy are applied to investigate alkaline
hydrolysis of aqueous K2[RuCl5H2O]. It is found that
on addition of a base ligand substitution is
accompanied by polycondensation processes which
afford filament structures consisting of Ru(OH)4Cl2
octahedra bonded by single OH-bridges. When
polynuclear compounds are sorbed on the surface of
carbonic substrates, the filaments aggregate into
nanosized particles which have a diameter of
approximately 2.0 nm with a narrow size distribution. THE CHEMICAL COMPOSITION AND
STRUCTURE OF SUPPORTED SULFATED
ZIRCONIA REGULATED SIZE
NANOPARTICLES V.V. Kanazhevskii, V.P. Shmachkova,
N.S. Kotsarenko, D.I. Kochubey, J.C. Vedrine*
(*Laboratoire de Physico-Chimie des Surfaces,
ENSCP, Paris, France) AIP Conference Proceedings,
X-Ray Absorption Fine Structure - XAFS13,
882 (2007) pp. 648-650. A set of model skeletal isomerization catalysts —
sulfated zirconia nanoparticles of controlled thickness
anchored on different supports — was prepared using
colloidal solutions of Zr salt on titania as support. The
nanoparticles of zirconia (1–5 nm) are epitaxially
connected to the support surface, with S/Zr ratio
equals to 1.3–1.5. It was shown by EXAFS that
nanoparticles of non-stoichiometric zirconium sulfate
Zr(SO4)1+x, where x<0.5, are formed on the support
surface. Its structure looks like half-period shifted
counterdirected chains built-up by zirconium atoms
linked by triangle pyramids of sulfate groups.
Considering catalytic data of skeletal n-butane
isomerisation at 150°C, one can suggest that these
species behave as the active component of sulfated
zirconia. They are formed in subsurface layers as
zirconium hydroxide undergoes sulfation followed by
thermal treatment. SYNTHESIS OF NICKEL-DOPED ALKALI
HALIDE MICROCRYSTALS AND THEIR
SPECTRAL AND STRUCTURAL ANALYSIS Yu.G. Konyukhova*, V.I. Kochubei*,
D.I. Kochubey, V.P. Babenko (*Chernyshevskii
State University, Saratov, Russia) J. Struct. Chem.,
48(6) (2007) pp. 1099-1104. Nickel-doped alkali
halide microcrystals were obtained by various
methods, including an original synthetic procedure.
Their spectral and structural characteristics were
investigated. The crystal field strength was calculated
from the reflection spectra recorded for the
microcrystals for different impurity concentrations. In
contrast to single crystals, higher impurity
concentrations can be obtained for lower degrees of
aggregation in microcrystals. MODIFICATION OF
METHYLALUMINOXANE-ACTIVATED
ANSA-ZIRCONOCENE CATALYSTS WITH
TRIISOBUTYLALUMINUM -
TRANSFORMATIONS OF REACTIVE
CATIONS STUDIED BY NMR SPECTROSCOPY D.E. Babushkin, H.H. Brintzinger* (*Fachbereich
Chemie, Universität Konstanz, Konstanz, Germany) Chem. Eur. J.,
13(18) (2007) pp. 5294-5299. When triisobutylaluminum (AliBu3) is added to
solutions containing methylaluminoxane (MAO) and
rac-[Me2Si(ind)2ZrCl2] (ind: indenyl) in C6D6, NMR
spectra show that methyl-bridged mixedalkylaluminum
dimers Al(μ-Me)2Me4-xiBux
predominate. These dimers react with MAO under
partial transfer of isobutyl groups and induce a
conversion of the initially prevailing cationic
trimethylaluminum adduct
rac-[Me2Si(ind)2Zr(μ-Me)2Al
Me2+] to
rac-[Me2Si(ind)2Zr(μ-Me)2AlMeiBu+] and
rrac-[Me2Si(ind)2Zr(μ-Me)2AliBu2 +]. These species are
unstable and release isobutene under formation of
zirconocene hydrides. STATE OF RHODIUM(III) IN SULFURIC ACID
SOLUTIONS A.V. Belyaev*, M.A. Fedotov,
S.N. Shagabutdinova* (*Nikolaev Institute of
Inorganic Chemistry, Novosibirsk, Russia) Russ. J. Coord. Chem.,
33(2) (2007) pp. 136-139. The formation of rhodium(III) sulfate complexes
under moderately rigorous temperature conditions was
studied by 103Rh and 17O NMR spectroscopy. The
complexes [Rh2(μ-SO4)2(H2O)8]2+,
[Rh2(*μ-SO4)(H2O)8]4+, and [Rh3(μ-SO4)3
(μ-OH)(H2O)10]2+ were found to be the most stable
species in aged solutions. THE STUDY OF INDUCED AQUATION
OF Rh(III) SULFATE COMPLEXE S.N. Shagabutdinova*, M.A. Fedotov,
A.V. Belyaev* (*Nikolaev Institute of Inorganic
Chemistry, Novosibirsk, Russia) Russ. J. Coord. Chem.,
33(2) (2007) pp. 140-144. The processes of aquation of Rh(III) complexes in
the presence of BaCl2 and Ba(ClO4)2 were studied by
the 103RH and 17O NMR methods. In the first case,
the final products were found to be the monomeric
aqua chloride complexes, while in the second case,
aqua hydroxo complexes were formed. The chloride
ions present in the system significantly increase the
process rate. COMPLEXATION OF Rh(III) IN DILUTED
SULFURIC ACID SOLUTIONS A.V. Belyaev*, V.D. Il’yashevich**,
E.I. Pavlova**, M.A. Fedotov,
S.N. Shagabutdinova* (*Nikolaev Institute of
Inorganic Chemistry, Novosibirsk, Russia;
**Krastsvetmet Co., Krasnoyarsk, Russia) Russ. J. Coord. Chem.,
33(6) (2007) pp. 449-453.Application of Physicochemical Methods for Characterization of Catalysts, Supports, Synthesized Substances and Materials
CHARACTERIZATION OF A Pd–Fe BIMETALLIC MODEL CATALYST
M.P. Felicissimo*, O.N. Martyanov, Th. Risse**, H.-J. Freund* (*University Sao Paulo, Sao Carlos, Brazil; **Fritz Haber Institute, Berlin, Germany)
Surf. Sci., 601(10) (2007) pp. 2105–2116.
Small bimetallic Pd-Fe particles supported on a well ordered alumina film grown on NiAl (110) were studied focusing on the geometric, electronic, adsorption, as well as magnetic properties. The morphology, growth mode and surface composition were investigated by combining scanning tunneling microscopy (STM), temperature-programmed desorption (TPD) and infrared spectroscopy (IRAs) using CO as a probe molecule. Information on the electronic properties of the bimetallic systems was obtained by means of X-ray photoelectron spectroscopy (XPS). These measurements were amended by in situ ferromagnetic resonance spectroscopy to address the magnetic properties of the bimetallic particles. The subsequent deposition of the metals at 300 K varying the order of metal deposition resulted in two distinct bimetallic systems. Pd deposited on existing Fe particles forms a shell, however, FMR and XPS suggest that intermixing of Pd and Fe occurs to some extent. For the reverse order, a larger amount of Fe is required to coat Pd particles, due to the strong tendency of Pd to segregate to the surface of the particles.
THERMALLY ACTIVATED DISSIPATION IN A NOVEL FOAMED Bi-BASED OXIDE SUPERCONDUCTOR IN MAGNETIC FIELDS
K.A. Shaykhutdinov*, D.A. Balaev*, S.I. Popkov*, A.D. Vasilyev*, O.N. Martyanov, M.I. Petrov* (*Kirenskii Institute of Physics, Krasnoyarsk, Russia)
Supercond. Sci. Technol., 20(6) (2007) pp. 491-494.
The transport properties of a novel foamed superconductor Bi1.8Pb0.3Sr1.9Ca2Cu3Ox have been studied. As the analysis of resistive transitions in a magnetic field shows, the dissipation follows a thermally activated flux creep model with the temperature-independent pinning potential in S-N-S-type Josephson junctions.
FMR FINE STRUCTURE - A TOOL TO INVESTIGATE THE SPATIAL MAGNETIC PHASE SEPARATION PHENOMENA IN MANGANITES
O.N. Martyanov, V.F. Yudanov, R.N. Lee*, N.V. Volkov**, K.A. Sablina** (*Budker Institute of Nuclear Physics, Novosibirsk, Russia; **Kirensky Institute of Physics, Krasnoyarsk, Russia)
Phys. Status Solidi (RRL), 1(1) (2007) pp. R22-R24.
An original approach is proposed to study the magnetic phase separation phenomenon. It is based on the registration of the noise-like FMR Fine Structure (FMR FS) caused by the magnetic interparticle dipoledipole interaction between spatially separated ferromagnetic regions. Data obtained for a La0.7Pb0.3MnO3 single crystal point to the existence of spatially separated ferromagnetic regions. It is shown that FMR FS of the La0.7Pb0.3MnO3 single crystal is temperature reversible and disappears at the maximum of magnetoresistance.
HIGHLY TEXTURED BISMUTH-CONTAINING HIGH-TEMPERATURE SUPERCONDUCTOR CERAMICS OBTAINED BY UNIAXIAL PRESSING IN LIQUID MEDIUM: FABRICATION AND PROPERTIES
M.I. Petrov*,**, D.A. Balaev*, I.L. Belozerova*, A.D. Vasil’ev*,**, D.M. Gokhfel’d*,**, O.N. Martyanov, S.I. Popkov*,**, K.A. Shaihutdinov*,** (*Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, Russia; **Reshetnev Siberian State Aerospace University, Krasnoyarsk, Russia)
Techn. Phys. Lett., 33(9) (2007) pp. 740-743.
A new method of fabricating textured ceramics with a composition of Bi1.8Pb0.3Sr1.9Ca2Cu3Ox is described, according to which the initial low-density ceramics is subjected to uniaxial pressing in a liquid medium followed by drying and annealing. Analysis of the X-ray diffraction and scanning electron microscopy data show evidence for a high degree of texture in high-temperature superconductor ceramics fabricated using the proposed method. The results of magnetic measurements indicate that the obtained material possesses anisotropy of the magnetic moment for the magnetic field H oriented parallel and perpendicular to the direction of uniaxial pressing. The textured ceramics also show high diamagnetic response for H parallel to the c axis of grains, which makes these ceramics promising materials for practical applications.
FERROMAGNETIC RESONANCE STUDY OF THIN FILM ANTIDOT ARRAYS: EXPERIMENT AND MICROMAGNETIC SIMULATIONS
O.N. Martyanov, V.F. Yudanov, R.N. Lee*, S.A. Nepijko**,***, H.J. Elmers***, R. Hertel****, C.M. Schneider****, G. Schönhense*** (*Budker Institute of Nuclear Physics, Novosibirsk, Russia; **Institute of Physics, Kiev, Ukraine; ***University Mainz, Mainz, Germany; ****Institute of Solid State Research IFF-6, Electronic Properties, Jülich, Germany)
Phys. Rev. B, 75(17) (2007) 174429 (6 pages).
The dynamic magnetic properties of twodimensional periodic Co antidot arrays were studied by X-band ferromagnetic resonance. The experimental results on geometrically scaled antidot arrays reveal a strong attenuation of the uniform ferromagnetic resonance mode in comparison to a continuous film, but an excitation of nonuniform in-plane spin-wave modes. Micromagnetic finite-element simulations show that the static magnetic structure in an antidot array depends on the direction of the external field with respect to the symmetry axes of the antidot lattice, even if the external field is strong enough to enforce a technically saturated magnetization state. The analysis gives evidence that characteristic inhomogeneities in the magnetization distribution around the antidots give rise to the changes of the resonance modes with the in-plane direction of the magnetization.
OXIDATION OF ALUMINA-SUPPORTED Co AND Co-Pd MODEL CATALYSTS FOR THE FISCHER-TROPSCH REACTION
T. Nowitzki*, A.F. Carlsson**, O.N. Martyanov, M. Naschitzki**, V. Zielasek*, T. Risse**, M. Schmal***, H.-J. Freund**, M. Bäumer* (*Universität Bremen, Bremen, Germany; Fritz- Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany; ***Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil)
J. Phys. Chem., 111(24) (2007) pp. 8566-8572.
Cobalt and bimetallic Co-Pd systems are wellknown Fischer-Tropsch catalysts. Compared to Co, the bimetallic systems exhibit an increased activity toward CO hydrogenation and methane conversion, attributed to resistance against oxidation. To study the oxidation behavior, model catalysts have been generated by depositing either Co or first Co and subsequently Pd onto a thin epitaxial alumina film grown on NiAl(110). Pure Co particles and bimetallic particles with a Co core and a Pd shell have been studied before and after exposure to oxygen and after thermal treatments, using X-ray photoelectron spectroscopy (XPS), temperature-programmed CO desorption (TPD), ferromagnetic resonance (FMR), and infrared reflection absorption spectroscopy (IRAS) in ultrahigh vacuum. Large doses of O2 (1000 langmuirs; 1 langmuir = 10-6 Torr.s) at 300 K lead to complete oxidation of Co particles. Upon annealing to temperatures above 530 K, XPS indicates that the cobalt oxide is mostly reduced by transfer of oxygen to the alumina support, resulting in its thickening. TPD, however, indicates the existence of persistent surface oxygen species, reducing the CO adsorption energy on the particles. Exposures to small doses of O2 (30-50 langmuirs) were also studied by a careful comparison of XPS, TPD, and FMR data. In this case, XPS indicates Co in a metallic state, whereas TPD and FMR indicate oxidic behavior. It is concluded that small amounts of non-stoichiometric subsurface oxygen or subsurface and surface oxygen are present which are not detectable in the Co 2p XPS signal but have a pronounced effect on the surface chemistry and the magnetism, i.e., on certain bulk properties. In the case of bimetallic Co/Pd particles, an incomplete Pd shell on the Co particles even promotes oxygen uptake, while only a complete Pd shell inhibits oxidation.
INVESTIGATION OF THE HYDROGEN CAPACITY OF COMPOSITES BASED ON ZnOCu
V.A. Trounov*, V.T. Lebedev*, A.E. Sokolov*, Yu.S. Grushko*, G. Török**, J. C. van den Heuvel***, É. Batyrev***, T.M. Yurieva, L.M. Plyasova (*Petersburg Nuclear Physics Institute, Gatchina, Russia; **Research Institute for Solid State Physics and Optics, Budapest, Hungary; ***University of Amsterdam, Amsterdam, The Netherlands)
Crystallogr. Rep., 52(3) (2007) pp. 474-478.
The composites ZnOCuH(D) saturated with hydrogen (deuterium) to a content of ~1 wt % are investigated by the neutron scattering methods. Upon cooling of the samples (the ZnO matrix containing Cu crystals ~10 nm in size) from 300 to 4 K, hydrogen (deuterium) is condensed on the cluster surface and penetrates inside the clusters in which the atomic hydrogen content with respect to copper can be as high as 30% at 20 K. Simultaneously, hydrogen fills nanopores of the ZnO matrix. It is revealed that, at temperatures of 90–300 K, approximately one-third of the hydrogen amount participates in the fast diffusion (the diffusion constant is approximately equal to 8 × 10-5 cm2/s) and the other two-thirds are immobilized. At 20 K, the fraction of mobile hydrogen decreases to ~10%. An analysis of the results obtained demonstrates that the energy barriers retaining hydrogen in defect regions are relatively low.
OPTICAL PROPERTIES AND MICROMORPHOLOGY OF THE ZrO2/Si FILMS, PREPARED BY ION BEAM SPUTTERING DEPOSITION
V.V. Atuchin*, V.Sh. Aliev*, V.N. Kruchinin, C.V. Ramana** (*Institute of Semiconductor Physics, Novosibirsk, Russia;**University of Michigan, Michigan, USA)
Fundament. Problems Modern Mater. Sci., 4(3) (2007) pp. 62-65.
ZrO2 films have been deposited on Si(100) by ion beam sputtering deposition (IBSD) at temperature T = 70°C. Film structure properties and ZrO2/Si interface were observed with reflection high energy electron diffraction (RHEED) and high resolution transmission electron microscopy (HRTEM). Optical properties of the film were studied by spectroscopic ellipsometry over the spectral range 250-900 nm.
MAGNETIC NANOPARTICLES BASED ON BORATE GLASSES DOPPED WITH Fe AND Mn
I.S. Edelman*, R.D. Ivantsov*, O.S. Ivanova*, O.A. Bayukov*, V.I. Zaikovskii (*Kirensky Institute of Physics, Krasnoyarsk, Russia)
Func. Mater., 13(2) (2006) pp. 293-299.
Magnetic properties, including magneto-optical Faraday Effect (FE) have been investigated in potassium-aluminum boron glasses doped with iron and manganese oxides. The formation of magnetic nanoparticles has been proved using high resolution electron microscopy. A wide variety of particle size, shape, structure and distribution in the matrix has been observed depending on the technological conditions. The narrow region of the conditions has been established providing formation of almost ideal manganese ferrite single crystals of about 40 nm size distributed rather homogeneously in the matrix. Therefore, the glasses can be considered as a nanocomposite material. Thanks to the low concentration of paramagnetic elements, the glasses kept the optical transparence and demonstrated high FE in the infrared and a part of the visible spectral regions, thus making it possible to develop a new magneto-optical material for the 1,0-1,5 μm spectral region.
FROM MOLTEN GLASS TO CRYSTALLIZABLE MELT: THE ESSENCE OF STRUCTURAL EVOLUTION
E.G. Tsvetkov*, A.V. Davydov*,**, A.I. Ancharov***, I.V. Yudaev (*Institute of Geology and Mineralogy, Novosibirsk, Russia; **Institute of Inorganic Chemistry, Novosibirsk, Russia; ***Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
J. Crystal Growth, 294(1) (2006) pp. 22-28.
Within the frames of the model concept an attempt is made to reveal the principal differences in the structural self-assembling of melts responsible for their crystallization or vitrification. Results of in situ synchrotron diffraction and Raman spectroscopic study of melts, NMR spectroscopy of glasses, and computer modeling of predominant arrangement of cation and anion components of melts with different compositions were used as an experimental basis. The notions of active crystal-forming part of melt were introduced which is an assembly of cation–anion associative complexes and “free” structure-forming cations, and its passive part, which is fragments of polycondensed anion groupings of various scales. Crystallization is interpreted as cooperative interaction caused by the formation of coordination spheres of “free” cations inside precursor clusters resulting from the crystal-forming part of melt.
ANALYSIS OF THE PHASE COMPOSITION OF HUMAN KIDNEY STONES IN MODEL OBJECTS WITH THE USE OF SYNCHROTRON RADIATION DIFFRACTION
A.I. Ancharov*, A.I. Nizovskii, S.S. Potapov**, T.N. Moiseenko***, I.V. Feofilov*** (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Institute of Mineralogy, Miass, Russia; ***Novosibirsk State Regional Clinical Hospital, Novosibirsk, Russia)
Bull. Russ. Acad. Sci.: Phys., 71(5) (2007) pp. 653–656.
The possibility of using synchrotron radiation for X-ray diffraction analysis of kidney stones directly in a human has been investigated. Experiments using a special phantom object imitating a human body have been performed. The experimental results obtained show that the significant thickness of the objects studied and the presence of liquids and biological polymers do not impose fundamental limitations on the possibility of in vivo synchrotron radiation diffraction analysis of human kidney stones.
MODEL EXPERIMENT OF IN VIVO SYNCHROTRON X-RAY DIFFRACTION OF HUMAN KIDNEY STONES
A.I. Ancharov*, S.S. Potapov**, T.N. Moiseenko***, I.V. Feofilov***, A.I. Nizovskii (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Institute of Mineralogy, Miass, Russia; ***The State Regional Clinical Hospital, Novosibirsk, Russia)
Nucl. Instrum. Methods Phys. Res., sec. A, 575(1-2) (2007) pp. 221-224.
The diffraction of synchrotron radiation (SR) was used to explore the phase composition of kidney stones placed into a specific object phantom, which imitated the human body. As an imitation of the patient breath, the kidney stone was moved vertically and rotated to an angle of 15° during the recording of the X-ray pattern. It was shown that rotation and displacement did not distort the X-ray pattern.
APPLICATION OF SYNCHROTRON RADIATION FOR THE STUDY OF NONSTOICHIOMETRIC OXYGENPERMEABLE PEROVSKITES BY MEANS OF X-RAY DIFFRACTION
U.V. Ancharova*, A.I. Ancharov**, N.Z. Lyakhov**, A.P. Nemudry*, E.B. Pyatiletova**, O.A. Savinskaya**, S.V. Tsybulya (*Budker Institute of Nuclear Physics, Novosibirsk, Russia; **Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Nucl. Instrum. Methods Phys. Res., sec. A, 575(1-2) (2007) pp. 144-148.
In the present work, applicability and advantages of the use of synchrotron radiation to the X-ray diffraction (XRD) study of the phase composition and microstructure of nonstoichiometric oxygenpermeable oxides having the composition Sr1−xAxCo0.8−yAlyFe0.2Oz, (where A=La, Ca) and SrFe1−xMxOz, (where M=W, Mo) have been demonstrated.
ADSORPTION OF MOLECULAR HYDROGEN ON ULTRAFINE MICROPOROUS/MESOPOROUS MATERIALS
V.Yu. Gavrilov
Kinet. Catal., 48(6) (2007) pp. 799-802.
The comparative processing of H2 adsorption isotherms obtained at 77 K is demonstrated to be applicable to the investigation of the microtexture of the ultrafine oxide materials MCM-41 and ZSM-5 and their mechanical mixtures. The H2 sorption method allows the micropore volume to be determined correctly for mixed ultrafine microporous/mesoporous materials.
SPECIFIC FEATURES OF THE COMPARATIVE ADSORPTION ANALYSIS OF THE TEXTURE OF ULTRAFINE MICROPOROUS/MESOPOROUS MATERIALS
V.Yu. Gavrilov, E.E. Sokolov
Kinet. Catal., 48(6) (2007) pp. 794-798.
N2 adsorption on the uniformly mesoporous material MCM-41, zeolite ZSM-5, and their mechanical mixtures at 77 K is reported. The use of the differential comparative method in the analysis of adsorption isotherms for this class of materials is complicated by the weak sorbate–MCM-41 surface adsorption interaction and, for adsorbent mixtures, by the compensation effect caused by the introduction of adsorption sites with an increased adsorption potential. Specific features of sorption on the twocomponent system are analyzed in the framework of the conventional BET model.
IDENTIFICATION OF GOLD OXIDE CLUSTER STRUCTURES IN Au/Al2O3 CATALYSTS FOR LOW-TEMPERATURE CO OXIDATION
V.F. Anufrienko, B.L. Moroz, T.V. Larina, S.Ph. Ruzankin, V.I. Bukhtiyarov, V.N. Parmon
Doklady Phys. Chem., 413(2) (2007) pp. 75-80.
The chemical state of gold in Au/Al2O3 catalysts prepared by different methods (incipient wetness technique or absorption of gold(III) hydroxide complexes) was studied by diffuse reflectance (DR) UV-vis spectroscopy. Modeling of the plasmon absorption by small metallic gold particles as well as quantum-chemical calculations of the electronic spectra of hypothetical dimeric [AuХ(μ2−O)(H2O)]2 (X = Cl или ОН) complexes by the density functional theory (DFT) method were performed for the assignment of the absorption bands in the DR UV-vis spectra of gold catalysts. Comparison between the experimental and calculated data shows that the Au/Al2O3 catalysts calcined in air at 400°С contain both metallic gold nanoparticles and gold oxide clusters chemically anchored onto the support surface.
DISTORTION OF THE TETRAHEDRAL COORDINATION OF Fe(III) IONS STABILIZED IN ZSM-5 ZEOLITE FRAMEWORK
S.E. Malykhin, V.F. Anufrienko, E.J.M. Hansen*, E.V. Kuznetsova, T.V. Larina, G.M. Zhidomirov (*Technical University Eindhoven, The Netherlands)
J. Struct. Chem., 48(5) (2007) pp. 855-861.
A simple qualitative method to analyze d-d-electronic transitions in cations of the transition elements in oxide matrices is proposed. In the particular case, all the excited states of interest differ only in the electronic configuration of d-orbitals, and the energies of transitions can be computed via the configuration interaction (CI) method restricted by the active space of five cation d-orbitals. An ordinary cluster model that takes into account the first coordination sphere of transition metal ion consisting of the framework of oxygen ions is sufficient for this purpose. The systematic overestimation error of transition energies can be corrected through the empirical factor calculated to fit experimental UV-vis spectra. The physical meaning of the scaling factor proposed is the dynamic part of electron correlation that remains unaccounted for in the chosen active CI space. The observed d-d-transitions of Fe3+ ions in MFI zeolites are analyzed in detail. It is suggested that the specifics of the observed electronic spectra are caused by the distortion of the tetrahedron of oxygen atoms around Fe3+. The latter can be easily taken into account when selecting an appropriate Fe3+ cluster model in the framework. It is shown that the occurrence of the weak low-frequency band below 21,000 cm−1 indicates the distortion of the tetrahedral environment around Fe3+.
STUDIES OF OXIDATIVE CAPACITY OF CERIUM-CONTAINING OXIDES OF VARIOUS COMPOSITIONS FOR CATALYSTS OF THE AUTOMOTIVE EXHAUST GASES CLEANING
A.V. Porsin*, E.A. Alikin*, N.M. Danchenko*, V.N. Rychkova*, M.Yu. Smirnov, V.I. Bukhtiyarov (*Ural Electrochemical Enterprise, Factory of Automobile Catalysts, Novouralsk, Russia)
Catal. Ind., 6 (2007) pp. 39-45.
Introducing of cerium-containing oxide components into the catalysts for exhaust gases purification leads to improving the catalyst action in the conditions of variable composition of redox gas mixture. Promotion action of cerium containing oxides is conditioned by their ability to accumulate and give back oxygen (during transition of Ce+3 and Ce+4) in dependence of partial pressure of oxygen in gas phase. The qualitative estimation of efficiency of the action of cerium containing component can be based on dynamic oxygen capacity. The dynamic oxygen capacity of cerium containing catalysts of various compositions: CeO2-δ; Ce0,8Zr0,2O2-δ; Ce0,65Zr0,2Pr0,15O2-δ; Ce0,8Nd0,2O2-δ and Ce0,8Gd0,2O2-δ was characterized with the purpose of election the most optimal component for the catalysts for exhaust gases purification. Specific surface, porosity, phase composition and structure of the synthesized oxides were characterized using XPS, XPA, PEEM. Dynamic oxygen capacity (OSC) of oxides was evaluated in temperature interval 250-500°C in reaction of CO + O2 oxidation based on data on degree of CO oxidation in the presence of mixed sample (Pt/Al2O2 + oxide) and of catalyst Pt/Al2O2 supported on cordierite block of honeycomb structure. It was stated that oxides Ce0,8Zr0,2O2-δ and Ce0,65Zr0,2Pr0,5O2-δ revealed the most dynamic oxygen capacity, low changes after hydrothermal ageing at 1050°C. These allowe these oxides to be recommend for the use for preparation of catalysts for cleaning of exhaust gases.
SMALL-ANGLE X-RAY CHARACTERIZATION OF THE NUCLEOPROTEIN COMPLEXES RESULTING FROM DNA-INDUCED OLIGOMERIZATION OF HIV-1 INTEGRASE
S. Baranova*, F.V. Tuzikov, O.D. Zakharova*, N.A. Tuzikova, Ch. Calmels**, S. Litvak**, L. Tarrago-Litvak**, V. Parissi**, G.A. Nevinsky* (*Institute of Chemical Biology and Fundamental Medicine, Novosibirsk, Russia; **UMR 5097 CNRS-Universite, Bordeaux cedex, France and IFR 66 Bordeaux, France)
Nucleic Acids Res., 35(3) (2007) pp. 975-987.
HIV-1 integrase (IN) catalyses integration of a DNA copy of the viral genome into the host genome. Specific interactions between retroviral IN and long terminal repeats (LTR) are required for this insertion. To characterize quantitatively the influence of the determinants of DNA substrate specificity on the oligomerization status of IN the small angle X-ray scattering (SAXS) technique was used. Under certain conditions in the absence of ODNs IN existed only as monomers. IN preincubation with specific ODNs led mainly to formation of dimers, the relative amount of which correlated well with the increase in the enzyme activity in the 30-processing reaction. Under these conditions, tetramers were scarce. Non-specific ODNs stimulated formation of catalytically inactive dimers and tetramers. Complexes of monomeric, dimeric and tetrameric forms of IN with specific and non-specific ODNs had varying radii of gyration (Rg), suggesting that the specific sequence-dependent formation of IN tetramers can probably occur by dimerization of two dimers of different structure. From data it can be concluded that the DNA-induced oligomerization of HIV-1 IN is probably of importance to provide substrate specificity and to increase the enzyme activity.
ELECTRONIC STRUCTURE OF HEAVY-ELEMENT OXIDES AND FLUORIDES: XANES LIII SPECTROSCOPY AND DFT CALCULATIONS
S.P. Gabuda*, S.G. Kozlova, V.A. Slepkov*, S.B. Erenburg*, N.V. Bausk* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Nucl. Instrum. Methods Phys. Res. A, 575(1-2) (2007) pp. 159-161.
XANES LIII spectra of series Tl, Pb and Bi compounds are studied. The data of DFT–ZORA calculations are in satisfactory agreement with the results of XANES spectroscopy of heavy-element fluorides and oxides. The fine structure of LIII absorption near edge for Tl3+, Pb4+ and Bi5+ ions is associated with transitions to the atomic 6s1/2, 6p1/2 (relativistic allowed) and 6d–7s terms. The “superfluous” lines observed in XANES spectra of Tl+, Pb2+ and Bi3+ oxides and fluorides are associated with the mix of 6s1/2 and 6p3/2 states of heavy 6s2 ions.
THE PREPARATION OF GOLD NANOPARTICLES IN TRITON N-42 REVERSE MICELLES AFTER PRELIMINARY CONCENTRATION FROM ACID SULFATE–CHLORIDE SOLUTIONS
A.I. Bulavchenko*, A.T. Arymbaeva*, O.A. Bulavchenko, V.V. Tatarchuk*, N.I. Petrova* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Russ. J. Phys. Chem., 80(12) (2006) pp. 1980-1985.
The distribution of Au(III) between an acid (3 mol/l HCl) aqueous phase and a micellar Triton N-42 solution in n-decane was studied as a function of the concentration of Na2SO4 (0–3.55 mol/l). The high distribution coefficients (200–500) allow 50-fold absolute concentration to be performed at a 90% extraction. Au0 nanoparticles were obtained by the injection solubilization of a reducing agent (hydrazine) into micellar extracts. At low solubilization capacities (≤1 vol %) and high reducing agent concentrations (≥0.2 mol/l) in Triton N-42 micelles, stable systems of Au0 nanoparticles suitable for the spectrophotometric determination of gold were obtained. At high solubilization capacities and low hydrazine concentrations, reduction was accompanied by coagulation and sedimentation processes. These processes were studied by spectrophotometry and the static and dynamic light scattering methods.
PHASE ANALYSIS OF PRODUCTS OF MECHANOCHEMICAL TREATMENT BY REFERENCE-FREE STOICHIOGRAPHY METHOD BASED ON THE DIFFERENTIAL DISSOLUTION
V.V. Malakhov, L.S. Dovlitova, A.A. Vlasov, N.N. Boldyreva
Chem. Sustain. Devel., 15(2-1) (2007) pp. 117-125.
Main principles of reference-free stoichiography method based on the Differential Dissolution (DD) are reported. This method allows determine stoichiometry and quantitative content of crystalline and amorphous substances of constant and variable composition without using reference samples of corresponding individual phases. High selectivity and sensibility of DD method, as well as special equipment provides simplicity and rapidity of DD-analysis of various objects. Products of mechanochemical treatment as usual are characterized by unknown phase composition, defect crystal or amorphous structure. Application of X-ray, IR spectroscopy and other methods for phase analysis often appears to be inefficient in these cases. At the same time DD method allows to solve most of problems appeared upon investigation of phase composition, structure and properties of such substances. At present this method is applied for investigation of about 20 systems, the results are summarized in the paper.
EFFECTS OF EVAPORATION AND MELTING ON NONSTOICHIOMETRY AND INHOMOGENEITY OF LiInSe2 CRYSTALS
I.G. Vasilyeva*, R.E. Nikolaev*, V.V. Malakhov, L.I. Isaenko** (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Institute of Mineralogy and Petrography, Novosibirsk, Russia)
J. Therm. Anal. Calorim., 90(2) (2007) pp. 601-605.
Evaporation and compositional changes of the liquids above the melting point of LiInSe2 crystals have been characterized quantitatively by using special techniques of a rapid thermal analysis and differential dissolution. The occurrence of a liquid immiscible region in the Li2Se-rich side of the Li2Se–In2Se3 diagram and incongruent evaporation with the preferential evaporation of In2Se3 rising markedly above boiling point were determined from the peaks on the thermal curves and from precise control over the composition of the vapour and residual solid as a function of temperature. It was shown that both the processes could be the sources of nonstoichiometry and inhomogeneity of the LiInSe2 crystals.
ACIDIC PROPERTIES OF FIBERGLASS MATERIALS
T.S. Glazneva, V.P. Shmachkova, L.G. Simonova, E.A. Paukshtis
React. Kinet. Catal. Lett., 92(2) (2007) pp. 303-309.
Acidic properties of fiberglass materials were investigated using the adsorption of NH3 and the rate of isopropanol dehydration. It is shown that the specific catalytic activity of such materials and amount of the Brönsted acid sites per their surface unit (100 Å2) exceed considerably those in zeolite HZSM-5.
DIRECT OBSERVATION AND MODELING OF ORDERED HYDROGEN ADSORPTION AND CATALYZED ortho–para CONVERSION ON ETS-10 TITANOSILICATE MATERIAL
G. Ricchiardi*, J.G. Vitillo*, D. Cocina, E.N. Gribov, A. Zecchina* (*Università di Torino, Torino, Italia)
Phys. Chem. Chem. Phys., 9(21) (2007) pp. 2753-2760.
Hydrogen physisorption on porous high surface materials is investigated for the purpose of hydrogen storage and hydrogen separation, because of its simplicity and intrinsic reversibility. For these purposes, the understanding of the binding of dihydrogen to materials, of the structure of the adsorbed phase and of the ortho–para conversion during thermal and pressure cycles are crucial for the development of new hydrogen adsorbents. The direct observation by IR spectroscopic methods of structured hydrogen adsorption on a porous titanosilicate (ETS-10) is reported, with resolution of the kinetics of the ortho–para transition, and an interpretation of the structure of the adsorbed phase based on classical atomistic simulations. Distinct infrared signals of o- and p-H2 in different adsorbed states are measured, and the conversion of o- to p-H2 is monitored over a timescale of hours, indicating the presence of a catalyzed reaction. Hydrogen adsorption occurs in three different regimes characterized by well separated IR manifestations: at low pressures ordered 1 : 1 adducts with Na and K ions exposed in the channels of the material are formed, which gradually convert into ordered 2 : 1 adducts. Further addition of H2 occurs only through the formation of a disordered condensed phase. The binding enthalpy of the Na+–H2 1 : 1 adduct is of –8.7 ± 0.1 kJ mol–1, as measured spectroscopically. Modeling of the weak interaction of H2 with the materials requires an accurate force field with a precise description of both dispersion and electrostatics. A novel three body force field for molecular hydrogen is presented, based on the fitting of an accurate PES for the H2–H2 interaction to the experimental dipole polarizability and quadrupole moment. Molecular mechanics simulations of hydrogen adsorption at different coverages confirm the three regimes of adsorption and the structure of the adsorbed phase.
ADSORPTION PROPERTIES OF OXIDIZED GALLIUM-MODIFIED ZEOLITE ZSM-5 FROM DIFFUSE REFLECTANCE IR AND QUANTUMCHEMICAL DATA. I. INTERACTION WITH HYDROGEN AND ETHANE
I.R. Subbotina*, N.A. Sokolova*, I.V. Kuz’min*, G.M. Zhidomirov, V.B. Kazanskii* (*Zelinskii Institute of Organic Chemistry, Moscow, Russia)
Kinet. Catal., 48(5) (2007) pp. 735-741.
Diffuse reflectance IR spectroscopy was used to study adsorption and subsequent high-temperature hydrogen and ethane transformations on gallium ions in gallium-modified ZSM-5 zeolite. The results were correlated with the corresponding quantum-chemical calculations. From the experimental and calculated data, it follows that trivalent gallium oxo ions are reduced to the univalent state in a hydrogen or ethane atmosphere even at moderate temperatures. Therefore, gallium oxo ions can function as active sites only at the early stages of light-paraffin aromatization. At the later stages, the dehydrogenation of light paraffins involves univalent gallium ions through the formation of intermediate gallium and alkylgallium hydrides.
BACTERIAL GENESIS OF CALCIUM PHOSPHATES IN HUMAN ORGANISM AND NATURE
L.G. Gilinskaya*, Yu.N. Zanin*, N.A. Rudina (*Trofimuk United Institute of Geology Geophysics and Mineralogy, Novosibirsk, Russia)
Lithology Mineral Resour., 42(1) (2007) pp. 56-67.
Comparison of natural marine (nodular and granular) carbonate-apatites and pathogenic mineral structures formed in human cardiac valves by methods of scanning electron and high-resolution transmission microscopy revealed common morphological features corresponding to the bacterial origin of calcium phosphates. These features may be considered typomorphic ones regardless of their formation environments (in vivo or in nature).
POTENTIALS OF GAS CHROMATOGRAPHY IN THE DETERMINATION OF REACTION PRODUCTS IN THE CATALYTIC OXIDATION OF AMMONIA TO NITROGEN(II) OXIDE
V.I. Zheivot, T.A. Nikoro, V.N. Krivoruchko, L.I. Panina, L.G. Pinaeva, L.A. Isupova
J. Anal. Chem., 62(12) (2007) pp. 1170-1175.
Peculiarities of the determination of nitrogen oxides and ammonia in the reaction products of ammonia oxidation are studied by gas chromatography. Particular attention was paid to the sampling problem. It is shown that in the course of the transportation of samples containing nitrogen(II) oxide and oxygen, the oxidation of nitrogen(II) oxide to nitrogen(IV) oxide takes place in the vapor phase. The conditions were found for suppressing or even eliminating the gas-phase reaction of NO oxidation to NO2 A procedure for the gas-chromatographic analysis of the reaction products in the catalytic oxidation of ammonia is proposed using several samples and packed columns, including the determination of NO with respect to NO2 formed in the gas-phase oxidation of NO.
MECHANOCHEMICAL SYNTHESIS OF SUPPORTED COPPER CATALYSTS FOR LACTIC ACID HYDROGENATION
I.L. Simakova, M.N. Simonov, V.N. Parmon, T.F. Grigorieva*, I.A. Vorsina*, A.P. Barinova*, N.Z. Lyakhov* (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Chem. Sustain. Devel., 15(2-1) (2007) pp. 169-173.
In the present work it was studied the opportunity of synthesis of nanodispersed copper catalysts by means of mechanochemical activation. The X-ray diffraction and IR-spectroscopy studies show, that interaction between aluminum and copper (II) oxide results in formation of dispersed metallic copper particles on the surface of alumina during very short activation time. The catalytic activity of obtained catalysts in lactic acid hydrogenation reaction is not high, but the selectivity of propylene glycol formation is significant. The mechanochemical activation of mixture of metallic copper and copper (II) oxide results in formation of copper (I) oxide that doesn’t show catalytic activity even after reductive activation.
LiCoO2-SUPPORTED CATALYSTS FOR HYDROGEN GENERATION FROM SODIUM BOROHYDRIDE SOLUTION
O.V. Komova, V.I. Simagina, N.V. Kosova*, O.V. Netskina, G.V. Odegova, T.Yu. Samoilenko, E.T. Devyatkina*, A.V. Ishchenko (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk Russia)
Chem. Sustain. Devel., 15(2) (2007) pp. 181-187.
Effect of LiCoO2 support prepared by traditional ceramic and mechanochemical route on the activity of Rh and Pt catalysts in the reaction of NaBH4 hydrolysis was studied and compared with traditional supports, such as γ-Al2O3, TiO2 (anatase) and carbon (sibunit). Catalysts supported on LiCoO2 prepared using mechanical activation were found to have the highest catalytic activity. However, the endurance tests of 1 % Rh-LiCoO2 and 1 % Pt-LiCoO2 catalysts showed their gradual degradation. To understand the reason of this phenomenon, the interaction of LiCoO2 with NaBH4 solution was studied by XRD, FTIR, DRS and TEM.
EFFECT OF THE NATURE OF THE ACTIVE COMPONENT AND SUPPORT ON THE ACTIVITY OF CATALYSTS FOR THE HYDROLYSIS OF SODIUM BOROHYDRIDE
V.I. Simagina, P.A. Storozhenko*, O.V. Netskina, O.V. Komova, G.V. Odegova, T.Yu. Samoilenko, A.G. Gentsler (*State Research Institute of Chemistry and Technology of Organoelement Compounds, Moscow, Russia)
Kinet. Catal., 48(1) (2007) pp. 168-175.
The effect of the nature of an active component and a support on the rate of hydrolysis of aqueous sodium borohydride solutions was studied. It was found that the activity of supported catalysts, which were reduced in a reaction medium of sodium borohydride, decreased in the order Rh > Pt ≈ Ru ≥ Pd regardless of the nature of the support (γ-Al2O3, a Sibunit carbon material, or TiO2). The catalysts based on TiO2 exhibited the highest activity. As found by UV–vis diffuse reflectance spectroscopy, the composition and structure of the supported precursor of an active component depend on the nature of the support. It is likely that rhodium clusters with different reaction properties were formed on various supports under the action of a reaction medium.
REGULARITIES OF FORMATION OF CUBIC ZIRCONIA STABILIZED WITH CALCIUM, YTTRIUM, AND INDIUM OXIDES UNDER MECHANOCHEMICAL TREATMENT
D.A. Zyuzin, E.M. Moroz, N.A. Pakhomov, G.R. Karagedov* (*Institute of Solid-State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Bull. Russ. Acad. Sci.: Phys., 71(5) (2007) pp. 614-617.
An effect of the composition of reacting components during mechanochemical activation on the ZrO2 structure stabilized with additives of In2O3, CaO, and Y2O3 oxides has been revealed. It is established that mechanochemical activation of oxide mixtures leads to the formation of dispersed solid solutions based on cubic zirconia. It is shown that interaction depth of the components during mechanochemical activation increases in the series of oxides In2O3 < CaO < Y2O3.
FORMATION OF THE STRUCTURE OF CERIUM OXIDE-MODIFIED TITANIUM DIOXIDE
G.A. Zenkovets, A.A. Shutilov, V.Yu. Gavrilov, S.V. Tsybulya, G.N. Kryukova* (*GNF e.V., Berlin- Adlershof, Germany)
Kinet. Catal., 48(5) (2007) pp. 742-748.
The formation of the structure of titanium dioxide containing 3–15 wt % CeO2 in a wide temperature range (300–850°C) has been investigated by X-ray powder diffraction, electron microscopy, and adsorption methods. Modification of titanium dioxide with cerium oxide causes the formation of nanostructured Ce–Ti–O compounds consisting of incoherently intergrown fine anatase crystallites. The crystallites are separated by interblock boundaries in which cerium ions are stabilized. The nanostructure formed in the Ce–TiO2 oxide system stabilizes the anatase phase, prevents the sintering of anatase particles at high temperatures, and allows modified anatase to retain a larger specific surface area and a higher porosity upon heat treatment than pure titanium dioxide does.
THE STRUCTURAL GENESIS OF A COMPLEX (MoVW)5O14 OXIDE DURING THERMAL TREATMENTS AND ITS REDOX BEHAVIOR AT ELEVATED TEMPERATURES
G.A. Zenkovets, G.N. Kryukova*, V.Yu. Gavrilov, S.V. Tsybulya, V.F. Anufrienko, T.V. Larina, D.F. Khabibulin, O.B. Lapina, E. Rödel**, A. Trunschke**, T. Ressler**, R. Schlögl** (*GNF e.V., Berlin-Adlershof, Germany;**Fritz- Haber-Institut der MPG, Berlin, Germany)
Mater. Chem. Phys., 103(2-3) (2007) pp. 295-304.
The structural genesis of a Mo0.68V0.23W0.09 oxide with Mo5O14-like structure has been examined. A precursor prepared by spray-drying of mixed aqueous metal salt solutions was calcined in air and subsequently treated in helium at different temperatures. X-ray diffraction, HRTEM, 51V magic angle spinning (MAS) NMR, ESR, UV/vis DR spectroscopy and oxygen and hydrogen adsorption measurements have been applied to monitor the preparation procedure. It was found that a structure closely related to that of Mo5O14 already appears at nano-scale level after calcinations of the spray-dried precursor in air at 3500C. At this stage, the material comprises of crystalline particles less than 3 nm in size stabilized by an amorphous matrix. Further heating causes nanostructural rearrangements that lead to the formation of the final Mo0.68V0.23W0.09 oxide with phase-pure polycrystalline structure. Molybdenum and tungsten ions are hexavalent and coordinated in an octahedral environment. Furthermore, vanadium is present as V4+ and V5+ ions occupying octahedral and highly distorted trigonal pyramidal sites, respectively. According to the results of H2 and O2 adsorption the crystalline ternary oxide does not possess accessible micropores. Oxygen pulses at 450°C and reductive treatment with pure hydrogen at 300°C did not cause noticeable changes of the bulk structure thus indicating a remarkable structural stability of the complex MoVW oxide under redox conditions at elevated temperature.
SYNTHESIS OF ALUMINUM OXIDES FROM THE PRODUCTS OF THE RAPID THERMAL DECOMPOSITION OF HYDRARGILLITE IN A CENTRIFUGAL FLASH REACTOR. I. PHYSICOCHEMICAL PROPERTIES OF THE PRODUCTS OBTAINED BY THE CENTRIFUGAL THERMAL ACTIVATION OF HYDRARGILLITE
Yu.Yu. Tanashev, E.M. Moroz, L.A. Isupova, A.S. Ivanova, G.S. Litvak, Yu.I. Amosov, N.A. Rudina, A.N. Shmakov, A.G. Stepanov, I.V. Kharina, E.V. Kulko, V.V. Danilevich, V.A. Balashov, V.Yu. Kruglyakov, I.A. Zolotarskii, V.N. Parmon
Kinet. Catal., 48(1) (2007) pp. 153-161.
A variety of physicochemical methods were used to characterize the product of the rapid thermal decomposition of hydrargillite in a centrifugal flash reactor under the following conditions: the average particle size of the reactant, 80–120 μm; the temperature of the solid heating surface (plate or cylinder), 300-700°C; hot-zone residence time, ~1 s; transfer of the product to the cooled zone of the reactor. The composition of the product and the extent of decomposition of hydrargillite were determined as a function of the processing temperature. The centrifugal thermal activation (CTA) of hydrargillite affords an X-ray-amorphous, highly reactive product with a developed surface and a disordered and inhomogeneous porous structure. This structure is capable of forming different modifications of aluminum hydroxide and oxide. The properties of the CTA product are compared with the properties of the earlier reported hydrargillite rapid decomposition products obtained using a gaseous heat-transfer agent (thermochemical activation product) or a fluidized bed of a granular heat transfer agent (thermal dispersion product).
SYNTHESIS OF ALUMINUM OXIDES FROM THE PRODUCTS OF THE RAPID THERMAL DECOMPOSITION OF HYDRARGILLITE IN A CENTRIFUGAL FLASH REACTOR. II. STRUCTURAL AND TEXTURAL PROPERTIES OF ALUMINUM HYDROXIDE AND OXIDE OBTAINED FROM THE PRODUCT OF THE CENTRIFUGAL THERMAL ACTIVATION OF HYDRARGILLITE (CTA PRODUCT)
E.V. Kulko, A.S. Ivanova, V.Yu. Kruglyakov, E.M. Moroz, K.I. Shefer, G.S. Litvak, G.N. Kryukova*, Yu.Yu. Tanashev, V.N. Parmon (*GNF e.V., Berlin-Adlershof, Germany)
Kinet. Catal., 48(2) (2007) pp. 316-326.
The basic properties of aluminum hydroxide compounds, namely, the flash product and the centrifugal thermal activation (CTA) product both before and after heat treatment at 400–1100°C are considered. The hydration conditions for obtaining 100% pseudoboehmite from the CTA product are determined. The structure, morphology, and texture of pseudoboehmite aluminum hydroxide synthesized from the CTA product and of the aluminum oxides obtained from this hydroxide in the temperature range 600–1100°C are described.
SYNTHESIS OF ALUMINUM OXIDES FROM THE PRODUCTS OF THE RAPID THERMAL DECOMPOSITION OF HYDRARGILLITE IN A CENTRIFUGAL FLASH REACTOR. III. PROPERTIES OF ALUMINUM HYDROXIDES AND OXIDES OBTAINED VIA THE MILD REHYDRATION OF THE PRODUCTS OF THE CENTRIFUGAL THERMAL ACTIVATION OF HYDRARGILLITE
I.V. Kharina, L.A. Isupova, G.S. Litvak, E.M. Moroz, G.N. Kryukova*, N.A. Rudina, Yu.Yu. Tanashev, V.N. Parmon (*GNF e.V., Berlin- Adlershof, Germany)
Kinet. Catal., 48(2) (2007) pp. 327-335.
The interaction between the amorphous product of the centrifugal thermal activation of hydrargillite (CTA HG) and aqueous electrolytes (pH 5–11) under mild conditions (15–35°C, atmospheric pressure) has been investigated by a variety of physicochemical methods. This interaction causes material morphologic and phase changes in CTA HG, and the product composition is governed by the pH of the electrolyte and by the hydration temperature and time. The product that forms in a basic medium or water in < 24 h contains up to 50% pseudoboehmite. Raising the pH or temperature or extending the hydration time results in the formation of bayerite as the major phase (~80%). An X-ray amorphous hydroxide forms in acid media. The heat treatment of this hydroxide at 550°C yields aluminum oxides differing from alumina prepared via hydroxide reprecipitation. Products with new, unusual properties can thus be obtained.
Ce-SILICA MESOPOROUS SBA-15-TYPE MATERIALS FOR OXIDATIVE CATALYSIS: SYNTHESIS, CHARACTERIZATION, AND CATALYTIC APPLICATION
M.N. Timofeeva, S.H. Jhung*, Y.K. Hwang*, D.K. Kim*, V.N. Panchenko, M.S. Melgunov, Yu.A. Chesalov, J.-S. Chang* (*Korea Research Institute of Chemical Technology, Daejeon, South Korea)
Appl. Catal., A, 317(1) (2007) pp. 1-10.
Cerium-containing mesoporous materials have been synthesized by hydrothermal method and characterized by IR, DR-UV–vis and DRIFT spectroscopy, XRD and N2 adsorption methods. It was established that the d100 and unit-cell (a0) parameter increase with the increase of cerium content up to 2% in SBA-15 and then tend to remain the same. According to DR-UV–vis spectroscopic data, an agglomeration of cerium atoms was observed in the form of fine CeO2 crystallites. Important factors affecting the catalytic activity of Ce-SBA-15, namely the effect of cerium content, the state of cerium ions, the state of silanol groups on the surface of Ce-SBA-15, and stability of the catalyst have been studied in the cyclohexanol and cyclohexene oxidation with hydrogen peroxide.
EFFECT OF OXALIC ACID CONTENT AND MEDIUM OF THERMAL TREATMENT ON PHYSICOCHEMICAL AND CATALYTIC PROPERTIES OF MoVTeNb OXIDE CATALYSTS IN PROPANE AMMOXIDATION
G.Ya. Popova, T.V. Andrushkevich, G.I. Aleshina, L.M. Plyasova, M.I. Khramov* (*Solutia Inc., Gonzalez, FL, USA)
Appl. Catal., A, 328(2) (2007) pp. 195-200.
Catalytic characteristics of MoV0.3Te0.23Nb0.12Ox catalysts in propane ammoxidation depend strongly on the quantity of oxalic acid present during slurry preparation and on the redox conditions during thermal treatment of the catalyst. Two stage thermal treatment (320°C in air, 600°C in He) and oxalate anion to niobium ratio in the slurry С2О4 2−/Nb = 3–5 have been shown to result in the catalysts with the best catalytic properties. Optimal catalysts have been found to contain M1 and M2 crystalline phases in the ratio of 3:1 or more. When the molar ratio С2О4 2−/Nb exceeds 3.5, tellurium is lost during calcination in He and other phases beside M1 and M2 are formed.
REINFORCED NICKEL AND NICKEL-PLATINUM CATALYSTS FOR PERFORMING THE THERMALLY COUPLED REACTIONS OF METHANE STEAM REFORMING AND HYDROGEN OXIDATION
M.M. Danilova, Z.A. Sabirova, N.A. Kuzin, V.A. Kirillov, N.A. Rudina, E.M. Moroz, A.I. Boronin
Kinet. Catal., 48(1) (2007) pp. 116-124.
The formation of composite nickel and nickelplatinum catalysts reinforced with steel gauze was studied. The catalysts were prepared by sintering powdered nickel metal and a supported nickel catalyst (GIAP-3 or NIAP-18) with a chromium oxide additive in the case of nickel-containing composite catalysts or by sintering powdered nickel, aluminum, and a supported platinum catalyst in the case of catalysts containing nickel-platinum. With the use of electron microscopy, mercury porosimetry, and X-ray electron probe microanalysis, it was found that a metal matrix, in the pores of which supported catalyst particles were distributed, was formed in the composite catalysts. The reinforced nickel catalysts prepared were active in the reaction of methane steam reforming, and the catalysts containing nickel-platinum were active in the reaction of hydrogen oxidation. An increase in the activity of reinforced nickel catalysts in the course of the reaction was found. It is believed that the increase of the activity was due to the reduction of nickel oxide from an inactive difficultto-reduce oxide film containing nickel and chromium oxides under the action of the reaction atmosphere.
DEPENDENCE OF THE PROPERTIES OF Ce-Zr-Y-La-M-O SYSTEMS ON SYNTHETIC CONDITIONS AND ON THE NATURE OF THE TRANSITION METAL M (Mn, Fe, Co)
G.A. Turko, A.S. Ivanova, L.M. Plyasova, G.S. Litvak, V.A. Rogov, E.M. Slavinskaya, I.A. Polukhina, A.S. Noskov
Kinet. Catal., 48(1) (2007) pp. 143-152.
The effects of synthetic conditions, component ratios, and the nature of the transition metal on the physicochemical and catalytic properties of Ce–Zr–Y–La–M–O (M = Mn, Fe, Co) systems are studied. The Ce–Zr–Y–La–M–O samples precipitated at ~23°C and calcined at 600°C are single-phase and are solid solutions with a fluorite structure, which persists upon calcination at 1150°C. The Ce–Zr–Y–La–Fe(Co)–O samples precipitated at 70°C and calcined at 1150°C consist of two solid solutions, one cubic, and the other tetragonal. The specific surface area (Ssp) of the samples precipitated at ~23°C and calcined at 600°C increases in the order Ce–Zr–Y–La–O < Ce–Zr–Y–La–Mn–O < Ce–Zr–Y–La–Co–O Ce–Zr–Y–La–Fe-O. The specific surface area of the samples precipitated at 70°C is independent of M and is ~110 m2/g. Calcination at 1150°C reduces Ssp approximately by two orders of magnitude. The TPR of the unpromoted systems in H2 proceeds in two steps at 600–650 and 750–840°C. The introduction of M decreases the reduction temperatures and gives rise to a lower temperature peak between 150 and 300°C. The most effective promoter is cobalt. The fluorite-type catalysts containing no noble metal are active in NO reduction (XNO ~ 100%) at Treact = 400–450°C. The cobalt-containing catalysts are the most active in the oxidation of CO (Xmax = 28%) and hydrocarbons (Xmax = 4.3%).
EFFECT OF THE CALCINATION TEMPERATURE ON THE PROPERTIES OF Fe2O3/SiO2 CATALYSTS FOR OXIDATION OF HYDROGEN SULFIDE
G.A. Bukhtiyarova, I.V. Delii, N.S. Sakaeva*, V.V. Kaichev, L.M. Plyasova, V.I. Bukhtiyarov (*JSC Katalizator, Novosibirsk, Russia)
React. Kinet. Catal. Lett., 92(1) (2007) pp. 89-97.
The effect of the calcination temperature on the properties of supported iron oxide catalysts for hydrogen sulfide oxidation prepared by impregnation of silica with iron(III) nitrate has been studied. An increase in the calcination temperature was found to diminish the catalytic activity of the Fe2O3/SiO2 catalysts in hydrogen sulfide oxidation. This behavior can be explained by the agglomeration of iron oxide particles and by a decrease in the surface concentration of active sites. It has been shown that an increase in the calcination temperature makes the catalyst more stable towards the sulfidation of the active component (Fe2O3) to the iron disulfide phase.
SELF-PROPAGATING SYNTHESIS OF Pd-CeO2/Al2O3 AUTOMOTIVE MONOLITH CATALYSTS
U.F. Zav’yalova*, P.S. Barbashova**, A.S. Lermontov*, N.B. Shitova**, V.F. Tret’yakov*, T.N. Burdeinaya*, V.V. Lunin*, V.A. Drozdov**, S.A. Yashnik, Z.R. Ismagilov, P.G. Tsyrul’nikov** (*Topchiev Institute of
Petrochemical Synthesis, Moscow, Russia; **Institute of Hydrocarbons Processing, Omsk, Russia)
Kinet. Catal., 48(1) (2007) pp. 162-167.
Pd–CeO2 catalysts on a monolith support with a honeycomb structure have been for the first time prepared by surface self-propagating thermal synthesis (SSTS). Decomposition routes for the cerium precursors are deduced from TG–DTA data and from the mass spectra of decomposition intermediates. The Pd-CeO2/Al2O3monoliths prepared by SSTS are more active in CO oxidation, total hydrocarbon oxidation, and nitrogen oxide reduction than the catalysts obtained by conventional impregnation. This is explained by the fact that the SSTS products have a larger specific surface area and their active component has a smaller particle size.REGULARITIES IN FORMATION OF HONEYCOMB STRUCTURAL BLOCK TEXTURE ON BASIS OF DIFFERENT OXIDE MATERIALS
S.A. Yashnik, I.P. Andrievskaya, O.V. Pashke, Z.R. Ismagilov, J.A. Moulijn* (*Delft University of Technology, Delft, The Netherlands)
Catal. Ind., 1 (2007) pp. 35-46.
Taken as an example of honeycomb structure carriers on the basis of aluminum oxide, the effects of the nature of oxide component, blinder, modifying agents and thermal treatment temperature (as high as 1300°C) on phase composition, specific surface, porous texture, and mechanical strength of ceramic materials are studied. The main regularities of texture formation were found using mercury porosimetry, XRD, SEM, and others. It has been shown that the textural changes of monolith samples are shown to be mostly caused by removal of capillary water (20-100°C), disappearance of small pores and consolidation of oxide particles (100-700°C), and phase transformation of oxide component or blinder (900-1300°C). Knowledge of the mechanism and the features of aluminum, titanium, zirconium and alumosilicate based honeycomb material texture formation allow giving the practical recommendations to select binding components and modifying additives as well as the carrier drying and thermal treating conditions thereby providing a necessary complex of operational properties: porous structure, specific surface, and mechanical strength. Using the dependences obtained, it is possible to control the textural properties of the honeycomb carriers on the basis of aluminum, titanium, zirconium oxides in a wide range of values, thus expanding the field of their application.
DEVELOPMENT OF MONOLITHIC CATALYSTS WITH LOW NOBLE METAL CONTENT FOR DIESEL VEHICLE EMISSION CONTROL
S.A. Yashnik, Z.R. Ismagilov, A.V. Porsin*, S.P. Denisov*, N.M. Danchenko* (*Ural Electrochemical Integrated Plant, Novoural’sk, Russia)
Top. Catal., 42-43(1-4) (2007) pp. 465-469.
The chemical composition of the catalyst containing Mn–Al–O and Pt has been developed on the basis of the synergetic effect of Pt and manganese oxides observed in the HC and CO oxidation reactions. This effect allows decreasing the Pt loading to 0.70 g/L in the catalytic systems of diesel engine exhaust gases and provides high activity in low temperature oxidation of light and heavy hydrocarbons, and high thermal stability. It has been found that the catalytic activity of Pt–Mn–Al monolithic catalysts in butane oxidation and DIESEL tests depends on the Pt precursor and Pt loading. At similar Pt loadings (1.06 g/L), the catalytic activity increases in the order H2PtCl6~H2[Pt(OH)6] < Pt(NO2)2(NH3)2. When one Pt precursor is used, the catalytic performance improves with Pt loading increase from 0 to 1.06 g/L, and being nearly constant at higher Pt loading (2.65 g/L).
CATALYTIC PROPERTIES OF BIMETAL CATALYSTS BASED ON DOUBLE TRANSITION METAL COMPLEXES FOR THE FISCHER-TROPSCH SYNTHESIS
A.A. Khassin, S.I. Pechenyuk*, D.P. Domonov*, T.P. Minyukova, G.K. Chermashentseva, G.N. Kustova, L.M. Plyasova (*Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, Apatity, Murmansk Region, Russia)
Chem. Sustain. Devel., 15(6) (2007) pp. 683-693.
Potentialities of preparation of bimetal Fe–Ni, Fe–Co and Co–Cu catalysts by thermolysis of double complex salts (salts comprising a complex cation of one metal and a complex anion of another metal) and their catalytic properties for FT synthesis were studied. Supporting the double complex salts [Ni(NH3)6]3[Fe(CN)6]2, [Co(NH3)6][Fe(CN)6] and [Co(NH3)6]2C2O4[Cu(C2O4)2]2 on aluminium hydroxide followed by thermolysis of the resulting composition was shown to allow 15–40 nm metal particles to be obtained as anchored on alumina surface. In the case of double Ni–Fe and Co–Fe complexes, the resulting bimetal catalysts are 15–16 nm in size with fcc and bcc structures, respectively. Destruction of the complexes follows several sequential exothermic stages. Bimetal bcc Fe-Co particles produced by thermolysis of [Co(NH3)6][Fe(CN)6] + Al(OH)3 composition demonstrate catalytic properties which are quite different from literature data on Co-Fe catalysts: They are less active to the secondary processes of olefin hydrogenation but very selective to olefins. An increase in the process pressure up to 10–20 atm results in a considerable changes in properties of the bimetal Co-Fe catalysts including a decrease in the selectivity to olefins and in the rate of the secondary process of steam CO conversion. Such a dependence is accounted for by changes in the structure of the catalytically active component under the action of the reaction medium.
INFLUENCE OF THE CONDITIONS OF MANUFACTURE OF NANOMERIC ZIRCONIUM DIOXIDE, STABILIZED WITH YTTRIUM OXIDE, ON ITS CATALYTIC PROPERTIES IN THE OXIDATION OF CO
G.R. Kosmambetova*, P.E. Strizhak*, E.M. Moroz, T.E. Konstantinova**, A.V. Gural’skii*, V.P. Kol’ko, V.I. Gritsenko*, I.A. Danilenko**, O.A. Gorban** (*Pisarzhevskii Institute of Physical Chemistry, Kyiv, Ukraine; ** Galkin Donets’k Physico-Chemical Institute, Donets’k, Ukraine)
Theor. Exp. Chem., 43(2) (2007) pp. 102-107.
The morphological and catalytic properties of samples of nanomeric zirconium dioxide, stabilized with yttrium oxide, manufactured via the effect of a UHF field during the process of drying precipitated zirconium hydroxide and calcination at temperatures from 300 to 1000°C, were studied. It was shown that the highest activity in the oxidation of CO occurred with 40 nm particles of zirconium dioxide prepared at 1000°C.
PROPERTIES OF FERROUS-OXIDE CATALYST FOR AMMONIA OXIDATION DEPENDING ON RAW MATERIALS USED
V.Yu. Kruglyakov, L.A. Isupova, N.A. Kulikovskaya, A.A. Marchuk, I.V. Kharina, S.V. Tsybulya, G.N. Kryukova*, E.B. Burgina, V.A. Sadykov (*GNF e.V., Berlin-Adlershof, Germany)
Catal. Ind., 2 (2007) pp. 46-53.
Effect of source raw material (which is prepared using sulphate or chloride technologies from commercial hematite) and Al2O3 – binder, prepared by re-precipitation or hydration of thermoactivated hydrargillite, on physical chemical properties (activity in ammonia oxidation reaction, durability and porous structure) of ferrous oxide catalyst for ammonia oxidation, IC-42-1, used in two-step process of ammonia oxidation in UKL-7 devices has been studied. The use of binder prepared by the hydration of thermoactivated hydrargillite has been shown to obtain the catalyst with a higher NO (II) yield with other conditions being the same. The use of «sulphate» α-Fe2O3 and calcination at 950°C provides better operation parameters of IC-42-1 catalyst. The results obtained are taken into account during preparation of industrial batches (up to 3 m3/year) of IC-42-1 catalyst, which is delivered for use in UKL-7 devices.
FORMATION OF SUPPORTED SIZE-CONTROLLED NANOPARTICLES OF SULFATED ZIRCONIA
V.P. Shmachkova, N.S. Kotsarenko, V.V. Kanazhevskii, G.N. Kryukova*, D.I. Kochubey, J. Vedrine** (*GNF e.V., Berlin- Adlershof, Germany; **Leverhulme Centre for Innovative Catalysis, Liverpool, UK)
React. Kinet. Catal. Lett., 91(1) (2007) pp. 177-185.
Methods of the preparation of catalysts for alkane skeletal isomerization based on uniform nanoparticles of sulfated zirconia anchored to different supports were investigated. These catalysts were characterized by using the ICP, HRTEM and BET techniques. The activities of the catalysts in the reaction of n-butane isomerization were measured and compared with those of bulk catalysts.
STUDY OF PALLADIUM CATALYST DEACTIVATION IN SYNTHESIS OF 4,10-DIFORMYL-2,6,8,12-TETRAACETYL- 2,4,6,8,10,12-HEXAAZAISOWURTZITANE
A.P. Koskin, I.L. Simakova, V.N. Parmon
React. Kinet. Catal. Lett., 92(2) (2007) pp. 293-302.
Polycyclic nitramine hexanitrohexaazaisowurtzitane (HNIW, CL-20) is synthesized via hydrodebenzylation of a precursor over palladium-based catalyst. In the present work, it was studied the influence of the synthesis method of the palladium-based catalyst on the catalyst behavior during the hydrodebenzylation reaction of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12- hexaazatetracyclo[5.5.0.03,11.05,9] dodecane.
SPECIFIC FEATURES OF THE INTERACTION OF ALUMINIUM POWDER WITH WATER IN THE PRESENCE OF SURFACTANTS
A.I. Ratko*, T.F. Kuznetsova*, V.E. Romanenkov*, S.I. Eremenko*, S.F. Tikhov, D.F. Khabibulin, O.B. Lapina, V.A. Sadykov (*Institute of General and Inorganic Chemistry, Minsk, Belarus)
Herald of Belarusian Ac. Sci., 2 (2007) pp. 27-33.
Kinetic and high-resolution solid state NMR (27Al, 1H) studies of the interaction of aluminium powder (ASD-1) with water demonstrated that the influence of surfactants on the alumina conversion depends on the specific reactivity of alumina and on the surfactant nature. Two reaction regions were identified: kinetic (oxidation rate is higher in solutions than in water) and diffusion (aluminium conversion is higher in water than in solutions). Surfactants were discovered to favor amorphization of the products of hydrothermal oxidation of aluminium, a decrease in the surface area and pore expanding in alumina. The method of statistical sorption of tetrachloromethane vapor revealed the transformation of hysteresis loop in the adsorption-desorption isotherms under the action of various surfactants that indicates reshaping of alumina mesopores.
ACTIVATED ALUMINUM: FEATURES OF PRODUCTION AND APPLICATION IN THE SYNTHESIS OF CATALYSTS FOR PERTOCHEMISTRY AND OIL PROCESSING
M.V. Trenikhin*, A.G. Kozlov**, A.I. Nizovskii, V.A. Drozdov*, A.V. Lavrenov*, A.V. Bubnov*, V.P. Finevich*, V.K. Duplyakin* (*Institute of Hydrocarbon Processing, Omsk, Russia; **Omsk Division of the Institute of Semiconductors, Omsk, Russia)
Russ. J. General Chem., 77(12) (2007) pp. 2320-2327.
The best known procedures for aluminum activation are discussed and systematized. The analysis of published data and of results of the proper physicochemical research reveals that the phenomena of surface distribution, intergrain penetration and the internal diffusion in the crystal grains underlie the nature of aluminum activation with liquid metal alloys based on gallium. The experimental investigation using X-ray fluorescent spectroscopy of diffusion processes in the systems Al-Ga-In were performed for the first time. The procedures for formation of catalytically active complexes of AlCl3 type by treating the activated aluminum in situ in reaction media with chlorinated hydrocarbons were considered.
DESIGN OF SCHIFF BASE-LIKE POSTMETALLOCENE CATALYTIC SYSTEMS FOR POLYMERIZATION OF OLEFINS
N.A. Pakhomov, A.M. Volodin, S.V. Bogdanov, V.A. Averyanov*, S.A. Batashev* (Tula State University, Tula, Russia)
Proceed. Tula State University, ser. Chem., 6 (2006) pp. 235-241.
The effect of rehydration of nanodisperse alumina aerogel (amorphous alumina) in water vapor medium results in the formation of pseudoboehmite. The following dehydration of pseudoboehmite results in the formation of disperse γ-Al2O3 which is stable to water vapor at temperatures below 100°C.
PREPARATION OF PURE MONODISPERSE CALCIUM CARBONATE PARTICLES
A.I. Lysikov, A.N. Salanov, E.M. Moroz, A.G. Okunev
React. Kinet. Catal. Lett., 90(1) (2007) pp. 151-157.
The non-template synthesis of monodisperse spherical particles of calcium carbonate is reported. Particles of a 3.5–4.5 μm size were produced by precipitation of calcium carbonate from alcohol solution at subzero temperatures.
SUPERCRITICAL CO2 ASSISTED SYNTHESIS OF HIGHLY SELECTIVE NAFION–ZEOLITE NANOCOMPOSITE MEMBRANES FOR DIRECT METHANOL FUEL CELLS
E.N. Gribov, E.V. Parkhomchuk, I.M. Krivobokov, J.A. Darr*, A.G. Okunev (*Department of Materials, Queen Mary University of London, London, UK)
J. Membr. Sci., 297(1-2) (2007) pp. 1-4.
The synthesis of nafion–zeolite (Fe-silicalite-1) nanocomposite membranes is reported using either a supercritical CO2 pre-treatment followed by impregnation with zeolite nanoparticles or in situ synthesis of Fe-silicalite-1 inside the pores of nafion membrane. The effects of the supercritical CO2 activation and the size of embedded zeolite particles on the proton conductivity and methanol permeability of composite membranes are observed. In selected cases, the membranes exhibit extremely low methanol permeability and high selectivity (defined as proton conductivity/methanol permeability ratio).
FULL PHENOL PEROXIDE OXIDATION OVER Fe-MMM-2 CATALYSTS WITH ENHANCED HYDROTHERMAL STABILITY
M.N. Timofeeva, M.S. Melgunov, O.A. Kholdeeva, M.E. Malyshev, A.N. Shmakov, V.B. Fenelonov
Appl. Сatal. B., 75(3-4) (2007) pp. 290-297.
Iron-containing mesoporous mesophase materials Fe-MMM-2 have been synthesized by a sol-mesophase route under mild acidic conditions and characterized by DRS-UV-vis, XRD, and N2 adsorption measurements. It was found that pH of the synthesis solution and iron content in the samples affect both the textural characteristics and the state of iron atoms. Isolated iron species predominate in silica framework under Fe < 2 wt. % and pH ~ 1.0 or Fe ~ 1 wt. % and pH < 2.0. These species are stable to leaching and highly active in full H2O2-based phenol oxidation. The increase in iron loading and pH of the synthesis solution lead to the agglomeration and formation of oligomeric iron species, which, in turn, results in the reduction of the catalytic activity of Fe-MMM-2 and the increase of iron leaching.
PREPARATION AND CHARACTERISATION OF PALLADIUM-LOADED POLYPROPYLENE POROUS HOLLOW FIBRE MEMBRANES FOR HYDROGENATION OF DISSOLVED OXYGEN IN WATER
R. van der Vaart*, V.I. Lebedeva**, I.V. Petrova**, L.M. Plyasova, N.A. Rudina, D.I. Kochubey, G.F. Tereshchenko**, V.V. Volkov**, J. van Erkel* (*TNO Science & Industry, Apeldoorn, The Netherlands; **Topchiev Institute of Petrochemical Synthesis, Moscow Russia)
J. Membr. Sci., 229(1-2) (2007) pp. 38-44.
Dissolved oxygen is one of the major components to be removed for the production of ultra-pure water. For the removal of oxygen to very low levels (less than 1 ppb for rinse water for the semiconductor industry), the catalytic reduction with hydrogen is an attractive method. The objective of this study was to integrate the palladium catalyst with the shell side of hydrophobic porous polypropylene membrane hollow fibre membranes to obtain a compact and efficient technique that preferably can be based on commercially available materials and modules. It was demonstrated that palladium could be deposited on a hydrophobic porous membrane hollow fibre, while maintaining its hydrophobic nature. Palladium loadings as low as 0.36% (w/w) were sufficient to catalyse the hydrogenation of dissolved oxygen while maintaining diffusion limited kinetics. Hence, a fast oxygen removal system is obtained that has the potential of maintaining removal rate, even at very low oxygen concentrations.
REACTIONS OF ELEMENTAL PHOSHORUS AND PHOSPHINE WITH ELECTROPHILES IN SUPERBASIC SYSTEMS. XIX. FORMATION OF THE C-P BOND WITH PARTICIPATION OF ELEMENTAL PHOSPHORUS UNDER MICROWAVE ASSISTANCE
S.F. Malysheva*, N.K. Gusarova*, V.A. Kuimov*, B.G. Sukhov*, A.A. Kudryavtsev*, O.G. Sinyashin**, Yu.G. Budnikova**, Z.P. Pai, A.G. Tolstikov, B.A. Trofimov* (*Favorsky Irkutsk Institute of Chemistry, Irkutsk, Russia; **Arbuzov Institute of Organic and Physical Chemistry, Kazan, Tatarstan, Russia)
Russ. J. General Chem., 77(3) (2007) pp. 415-420.
Microwave irradiation facilitates phosphorylation of aryl methyl chlorides and styrene with red phosphorus in the presence of strong bases and increases the yield of the main products, tertiary phosphine oxides.
CHEMICAL AND OPTICAL PROPERTIES OF THE TITANIUM DIOXIDE PRODUCED FROM COMBUSTION OF TITANIUM MICROPARTICLES IN AIR
V.S. Zakharenko, V.N. Parmon, S.A. Khromova
Atmos. Oceanic Opt., 20(6) (2007) pp. 486-491.
It is shown that the solid titanium dioxide aerosol, obtained from combustion in air of a pyrotechnic mixture containing titanium microparticles, has optic, chemical, and photocatalytic properties similar to those of titanium dioxide produced in other ways. An aerosol cloud produced from such titanium dioxide immediately in the place of abrupt emission of pollution favors purification of the gas-phase atmosphere nearby the pollution source
SYNTHESIS AND CHARACTERIZATION OF MESOPOROUS SILICA THIN FILMS AS A CATALYST SUPPORT ON A TITANIUM SUBSTRATE
T.S. Glazneva, E.V. Rebrov*, J.C. Schouten*, E.A. Paukshtis, Z.R. Ismagilov (*Eindhoven University of Technology, Eindhoven, The Netherlands)
Thin Solid Films, 515(16) (2007) pp. 6391-6394.
Mesoporous silica films with a thickness of 500– 900 nm were synthesized on a titanium substrate by the evaporation-induced self-assembly method (with 900–1200 rpm for 90 s) using cetyltrimethylammonium bromide (CTAB) as structure-directing agent and tetraethyl orthosilicate as the silica source. Prior to coating deposition, the titanium substrate was oxidized to increase the surface roughness up to 500 nm and to produce a thin titania layer. Just before the synthesis, the titania layer was made super hydrophilic by an UV treatment for 2 h to provide a better adhesion of the silica film to the substrate. Films with hexagonal and cubic mesostructures with a uniform pore size of 2.8 nm and a surface area of 1080 m2/g were obtained and characterized by different methods. An alternative approach for surfactant removal by gradual heating up to 250°C in vacuum was applied. Complete removal of CTAB from the as-synthesized silica films was confirmed by infrared spectroscopy.
INFLUENCE OF CATALYSTS’ ACTIVATION ON THEIR ACTIVITY AND SELECTIVITY IN CARBON NANOTUBES SYNTHESIS
A.N. Usoltseva, V.L. Kuznetsov, N.A. Rudina, E.M. Moroz, M. Haluska*, S. Roth* (*Max Planck Institute for Solid State Research, Stuttgart, Germany)
Phys. Status Solidi B, 244(11) (2007) pp. 3920-3924.
In this paper the influence of catalysts' activation conditions on their selectivity in carbon nanotubes CVD synthesis by means of methane decomposition reaction using Fe- and FeCo-catalysts synthesized via polymerized complex rout providing homogeneous distribution of catalytic components have been investigated. It was shown that variation of catalysts' reduction conditions results in formation of different types of NTs (MWNTs or SWNTs). The most effective catalyst activation leading to formation of SWNTs consists in catalyst reduction by reaction mixture at high temperature. That can be explained in terms of carbon deposits nucleation on metals.
EVIDENCE OF AN EQUIMOLAR C2H2-CO2 REACTION IN THE SYNTHESIS OF CARBON NANOTUBES
A. Mager*, Jin W. Seo*, V.L. Kuznetsov, L. Forry* (*Institut de la Matière Complexe, EPFL, Lausanne, Switzerland)
Angewandte Chemie – Intern. Edition, 46(3) (2007) pp. 441-444.
Chemical vapor deposition (CVD) is considered to be the most viable process for the in situ production of nanotubes integrated into a device. Researchers have successfully attempted to control accurately the physical form of the carbon nanotubes produced. However, the method still suffers from low yields with respect to the carbon source and from high temperatures required for this conversion. A huge effort has been devoted to enhance the production efficiency at lower temperatures by modifying the catalyst (pregrowth chemical activation or by avoiding catalyst poisoning (e.g., by introducing an etching agent that prevents encapsulation by the precipitated amorphous carbon).
INFLUENCE OF HELIUM, HYDROGEN, OXYGEN, AIR AND METHANE ON CONDUCTIVITY OF MULTIWALLED CARBON NANOTUBES
A.I. Romanenko*,**, O.B. Anikeeva*,**, V.L. Kuznetsov, T.I. Buryakov*,**, E.N. Tkachev*,**, A.N. Usoltseva (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Novosibirsk State University, Novosibirsk, Russia)
Sens. Actuators, A, 138(2) (2007) pp. 350-354.
Temperature dependences of the conductivity of catalytic multiwalled carbon nanotubes (MWNTs) were measured in various gas environments: helium, hydrogen, oxygen, air and methane. It has been found that in the vicinity of the melting and vaporization temperatures of hydrogen, oxygen, air and methane the conductivity sharply decreases by (2–12%). The observed reversible change of the conductivity is connected with the adsorption–desorption of gases on the surface of nanotubes and breakup-recovery of contacts between nanotubes as a result of melting and vaporization of hydrogen, oxygen, air and methane.
SEPARATING WEAK-LOCALIZATION AND ELECTRON-ELECTRON-INTERACTION CONTRIBUTIONS TO THE CONDUCTIVITY OF CARBON NANOSTRUCTURES
E.N. Tkachev*,**, A.I. Romanenko*,**, O.B. Anikeeva*,**, T.I. Buryakov*,**, V.E. Fedorov*, A.S. Nazarov*, V.G. Makotchenko*, V.L. Kuznetsov, A.N. Usoltseva (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Novosibirsk State University, Novosibirsk, Russia)
Bull. NSU, ser. Physics, 2(3) (2007) pp. 76-80.
Effect of modification of curvilinear carbon nanostructures on the electrophysical properties was studied. A special synthesis technique was used to obtain multiwall catalytic carbon nanotubes (MWNTs) and expanded carbon that are practically free of amorphous carbon impurities. It makes possible to observe quadratic growth in the positive magnetoconductivity in the fields of up to B ~ 1 T, so called electron–electron interaction effects. They were unnoticeable in previously synthesized nanotubes.
SEPARATING WEAK-LOCALIZATION AND ELECTRON-ELECTRON-INTERACTION CONTRIBUTIONS TO THE CONDUCTIVITY OF CARBON NANOSTRUCTURES
E.N. Tkachev*,**, A.I. Romanenko*,**, O.B. Anikeeva*,**, T.I. Buryakov*,**, V.E. Fedorov*, A.S. Nazarov*, V.G. Makotchenko*, V.L. Kuznetsov, A.N. Usoltseva (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Novosibirsk State University, Novosibirsk, Russia)
J. Exper. Theor. Phys., 105(1) (2007) pp. 223-226.
The effect of the modification of curvilinear carbon nanostructures (nanotubes) on their electrical properties has been studied. The samples were prepared using a special method of synthesis, which excluded the formation of amorphous carbon particles in multiwalled carbon nanotubes and in expanded graphite. Such materials exhibit a quadratic growth in the positive magnetoconductivity in the fields of up to B ~ 1 T, which is not observed in the samples synthesized by usual methods.
ELECTRON–ELECTRON INTERACTION EFFECTS IN MULTIWALL CARBON NANOTUBES
E.N. Tkachev*,**, A.I. Romanenko*,**, O.B. Anikeeva*,**, V.L. Kuznetsov, A.N. Usoltseva (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Novosibirsk State University, Novosibirsk, Russia)
Low Temp. Phys., 33(2) (2007) pp. 272-275.
The temperature dependence of the electrical conductivity σ and the field dependence of the magnetoresistivity ρ of samples of multiwall catalytic carbon nanotubes containing a small amount of amorphous carbon impurity are studied. Below a temperature of 20 K the observed temperature dependence of the conductivity of the nanotubes shows a contribution from two-dimensional quantum corrections to the conductivity. At a temperature of 4.2 K one observes negative magnetoresistance on the ρ (B) curves in the field interval 0–10 kG, due to the dominance of the contribution to the magnetoresistance from the quantum corrections for interacting electrons. A special synthesis technique is used to obtain multiwall catalytic carbon nanotubes that are practically free of amorphous carbon impurities, making it possible to observe electron– electron interaction effects unnoticeable in previously synthesized nanotubes of this kind.
EFFECT OF GASES ON THE TEMPERATURE DEPENDENCE OF THE ELECTRIC CONDUCTIVITY OF CVD MULTIWALLED CARBON NANOTUBES
T.I. Buryakov*,**, A.I. Romanenko*,**, O.B. Anikeeva*,**, V.L. Kuznetsov, A.N. Usoltseva, E.N. Tkachev*,** (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Novosibirsk State University, Novosibirsk, Russia)
J. Exper. Theor. Phys., 105(1) (2007) pp. 155-159.
The influence of various gaseous media on the temperature dependence of the electric conductivity σ of multiwalled carbon nanotubes (MWNTs) synthesized using the method of catalytical chemical vapor deposition (CVD) has been studied. The σ(T) curves were measured in a temperature range from 4.2 to 300 K in helium and its mixtures with air, methane, oxygen, and hydrogen. The introduction of various gaseous components into a helium atmosphere leads to a significant decrease in the conductivity of MWNTs in the interval between the temperatures of condensation and melting of the corresponding gas. Upon a heating-cooling cycle, the conductivity restores on the initial level. It is concluded that a decrease in σ is caused by the adsorption of gases on the surface of nanotubes.
SOFT X-RAY SPECTROSCOPY AND QUANTUM CHEMISTRY CHARACTERIZATION OF DEFECTS IN ONION-LIKE CARBON PRODUCED BY NANODIAMOND ANNEALING
L.G. Bulusheva*, A.V. Okotrub*, V.L. Kuznetsov, D.V. Vyalikh** (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Dresden University of Technology, Dresden, Germany)
Diamond Relat. Mater., 16(4-7) (2007) pp. 1222-1226.
The electronic structure of onion-like carbon (OLC) consisted of quasi-spherical and polyhedral nanoparticles and produced as a result of nanodiamond annealing at 1800 K and 2140 K has been probed by soft X-ray emission and X-ray absorption spectroscopy. The enhanced density of states in the vicinity of the Fermi level was revealed for OLC prepared at moderate temperature. Ab initio calculation on carbon models showed the only unpaired electrons at the zigzag edges of graphitic fragments can provide localized states observed in the X-ray spectra. With the increase of the annealing temperature the defects, which likely constitute the boundaries of incompletely closed onion shells, are healing.
ENCAPSULATION OF MOLECULAR NITROGEN IN MULTIWALL CNX NANOTUBES
L.G. Bulusheva*, A.V. Okotrub*, A.G. Kudashov*, E.M. Pazhetnov, A.I. Boronin, D.V. Vyalikh** (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Dresden University of Technology, Dresden, Germany)
Phys. Stat. Sol. B, 244(11) (2007) pp. 4078-4081.
Multiwall CNx nanotubes have been grown in the result of acetonitrile decomposition over Fe catalyst (CVD method). The random nanotubes samples have been produced by classical technique using catalyst nanoparticles formed by iron bimaleate thermolysis. The aligned nanotubes have been synthesized by aerosol assisted CVD method where ferrocene was used as a catalyst source. X-ray photoelectron spectroscopy (XPS) showed the random sample contains two kinds of nitrogen, while additional highenergy peak was detected in the N 1s-spectrum of the aligned CNx nanotubes. X-ray absorption spectra measured near the N K-edge (NEXAFS) of the samples exhibited three peaks for both type of CNx nanotubes. The relative intensity of the high-energy peak was found to be much higher in the spectrum of aligned nanotubes. Assignment of the NEXAFS peaks was made using results of quantum-chemical calculations on carbon tube model incorporating pyridinic, three-fold coordinated and molecule nitrogen. The high energy peak was shown to correspond to N2 molecules and its absence in the XPS spectrum of random CNx nanotubes indicates the gaseous nitrogen is mainly concentrated in the interior region of nanotubes. The larger encapsulation of molecules in the aligned CNx nanotubes could be due to the higher diffusion of nitrogen atoms through the catalytic particles formed directly in the CVD process.
ATTENUATION OF ELECTROMAGNETIC WAVES IN ONION-LIKE CARBON COMPOSITES
S.A. Maksimenko*, V.N. Rodionova*, G.Ya. Slepyan*, V.A. Karpovich*, O. Shenderova**, J. Walsh**, V.L. Kuznetsov, I.N. Mazov, S.I. Moseenkov, A.V. Okotrub***, Ph. Lambin**** (*Institute for Nuclear Problem, Minsk, Belarus; **International Technology Center, Raleigh, USA; ***Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; ****Facultes Universitaires Notre-Dame de la Paix, Belgium)
Diamond Relat. Mater., 16(4-7) (2007) pp. 1231-1235.
The first results on measurements of electromagnetic wave attenuation of onion-like carbon (OLC) powders and OLC-based polymer films on a substrate are reported. The measurements cover a wide frequency range 2–38 GHz and demonstrate promising high potential of OLC-based composites as basic components for wideband electromagnetic wave absorbing materials. A description of the measurement technique is presented. Possibility and mechanisms of the absorption efficiency tuning are discussed.
SURFACE ELECTRONIC STRUCTURE OF DETONATION NANODIAMONDS AFTER OXIDATIVE TREATMENT
A.V. Okotrub*, L.G. Bulusheva*, I.S. Larionova**, V.L. Kuznetsov, S.L. Molodtsov***,**** (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **FGUP Federal Research and Production Centre Altay, Biysk, Russia; ***Dresden University of Technology, Dresden, Germany; ****St. Petersburg State University, St. Petersburg, Russia)
Diamond Related Mater., 16 (2007) pp. 2090-2092.
X-ray absorption spectroscopy has been used for comparative study of electronic structure of detonation nanodiamonds (ND) purified using different oxidative treatments. The treatment of detonation soot with a mixture of nitric and sulphuric acids followed by ion exchange and ultrafiltration of hydrosol obtained was found to result in developing of ND surface coverage consisting of oxidized carbon species, which electronic state is close to that of strongly oxidized graphite. The deeper purification of ND was demonstrated to allow cleaning of ND particles from most of the oxidized carbon contaminations.
NANODIAMOND AND ONION-LIKE CARBON POLYMER NANOCOMPOSITES
O. Shenderova*, T. Tyler*, G. Cunningham*, M. Ray*, J. Walsh*, M. Casulli*, S. Hens*, G. McGuire*, V.L. Kuznetsov, S. Lipa** (*International Technology Center, Raleigh, USA; **North Carolina State University, Raleigh, NC, USA)
Diamond Relat. Mater., 16(4-7) (2007) pp. 1213-1217.
The current work demonstrates that nanodiamond (ND) of detonation origin and onion-like carbon (OLC) are valuable additives in multifunctional polymer composites, particularly for polymers used in microelectronic applications. It is demonstrated that addition of ND to a polyimide matrix increases the thermal degradation temperature of the composites up to 30°C and also improves adhesion. The addition of 2 wt.% of ND increases thermal conductivity of PDMS up to 15%. Finally, it was also demonstrated that the addition of OLC to polydimethylsiloxane and polyurethane matrices increases the loss tangent of the composites.
THERMODYNAMIC ANALYSIS OF NUCLEATION OF BORON NITRIDE NANOTUBES ON METAL PARTICLES
V.L. Kuznetsov, I.N. Mazov, A.I. Delidovich*, E.D. Obraztsova**, A. Loiseau*** (*Novosibirsk State University, Novosibirsk, Russia; **Prokhorov General Physics Institute, Moscow, Russia; ***LEM, ONERA-CNRS, Chatillon, France)
Phys. Status Solidi B, 244(11) (2007) pp. 4165-4169.
Boron nitride nanotubes nucleation on the catalyst's surface after the formation of metal particle alloys oversaturated with boron and nitrogen atoms is the most important step for any type of the catalytic processes of BN nanotubes formation. A thermodynamic analysis of the boron-nitride nanotubes nucleation on the catalysts surface was performed. The master equations for the dependence of critical size of BN nucleus on reaction parameters, such as reaction temperature, supersaturation degree of catalyst particles with B and N, work of adhesion of catalyst to BN were obtained. These equations combined with the phase diagram approach can be used for the description of different scenarios of BN deposits formation and for the development of the main principles of catalysts design for BN nanotube production.
OXIDATIVE DEHYDROGENATION OF ETHYLBENZENE TO STYRENE OVER ULTRA-DISPERSED DIAMOND AND ONIONLIKE CARBON
D.S. Su*,***, N.I. Maksimova*, G. Mestl*, V.L. Kuznetsov, V. Keller**,***, R. Schlogl*,***, N. Keller**,*** (*Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany; **Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse, Strasbourg Cedex, France; ***European Laboratory for Catalysis and Surface Sciences)
Carbon, 45(11) (2007) pp. 2145-2151.
The catalytic properties of sp3-hybridized ultradispersed diamond and sp2-hybridized onion-like carbon in the oxidative dehydrogenation of ethylbenzene to styrene were investigated, highlighting the structure sensitivity of the reaction. The sp3-carbon led initially to C–C cleavage and benzene formation, while a switchover of the main reaction pathway into the styrene formation occurred with time on stream due to the formation of surface sp2 carbon, required for the selective styrene formation. This was confirmed by the behavior and the high stable styrene selectivity shown by onion-like carbons. High temperature oxygen pre-treatment created catalytically active species at the sp2 carbon surface, confirming that a high thermal stability carbon–oxygen complex was the active surface site for forming styrene.
STUDY OF THE ELECTRONIC STRUCTURE AND PROPERTIES OF 13C-ISOTOPE-BASED COMPOSITES
E.I. Zhmurikov*, A.I. Romanenko**,***, L.G. Bulusheva***, O.B. Anikeeva**,***, Yu.V. Lavskaya***, A.V. Okotrub***, O.G. Abrosimov, S.V. Tsybulya, P.V. Logachev*, L. Tecchio**** (*Budker Institute of Nuclear Physics, Novosibirsk, Russia; **Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; ***Novosibirsk State University, Novosibirsk, Russia; ****Istituto Nazionale di Fisica Nucleare, Rome, Italy)
J. Surf. Invest. X-Ray, Synchrotron Neutron Tech., 1(6) (2007) pp. 645-651.
The morphology and electronic structure of 13C-isotope-based graphite composites were studied by transmission electron microscopy (TEM), X-ray diffraction, and X-ray fluorescence spectroscopy. High-resolution TEM images showed that composites contain several forms of carbon particles. According to an x-ray diffraction analysis, the size of graphene stacks of graphite particles is 20 and 40 Å. The CKα X-ray fluorescence spectra of the initial 13C isotope powder and composites based on it detected an increase in the density of high-energy occupied states in comparison with the graphite spectrum. Ab initio quantum chemical calculation of the structure of C150 graphene showed that the increase in the density of states stems from the electrons of dangling bonds of boundary carbon atoms of particles ~20 Å in size. Electrical properties of 13C-isotope-based samples were studied by analyzing the temperature dependence of the conductivity. It was assumed that the change in the logarithmic dependence of the conductivity observed at liquid-helium temperatures to the linear dependence as the temperature increases is caused by carrier transfers between the disordered graphene layers forming a nanocomposite.
DIRECT SYNTHESIS OF NITROGENCONTAINING FILAMENTOUS CARBON ON A HIGH-PERCENTAGE Ni-Cu CATALYST
G.N. Ilinich, A.V. Romanenko, R.I. Kvon, V.B. Fenelonov, V.I. Zaikovskii, A.V. Ishchenko
Kinet. Catal., 48(1) (2007) pp. 103-115.
Nitrogen-containing catalytic filamentous carbon (N-CFC) of chemical composition NC18-NC104 has been synthesized by the decomposition of pyridine (Py) from gaseous mixtures with argon or H2 at 550- 800°C on Ni/Al2O3 (Ni) and Ni-Cu/Al2O3 (Ni–Cu) high-percentage catalysts. The activity of the Ni–Cu catalyst in Py decomposition in mixtures with H2 is about one order of magnitude higher than its activity in Py/Ar mixtures (more than 70 g N-CFC per metal gram in 4.5 h at 750°C), which is interpreted as arising from the nickel-catalyzed hydrogenation of Py. The formation and growth of carbon fibers occurs through the decomposition of Py (from Ar/Py mixtures) and/or Py hydrodenitrification products (from H2/Py mixtures). The carbon material has been characterized by elemental analysis, low-temperature nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The effect of the noncatalytic reactions of Py and its transformation products on the composition and texture of N-CFC is discussed.
SYNTHESIS OF NITROGEN-CONTAINING CARBON MATERIALS FOR SOLID POLYMER FUEL CELL CATHODES
Z.R. Ismagilov, A.E. Shalagina, O.Yu. Podyacheva, Ch.N. Barnakov*, A.P. Kozlov*, R.I. Kvon, I.Z. Ismagilov, M.A. Kerzhentsev (*Institute of Carbon and Carbon Chemistry, Kemerovo, Russia)
Kinet. Catal., 48(4) (2007) pp. 581-588.
The following nitrogen-containing supports with various nitrogen contents and structure and texture properties were synthesized: carbon nanofibers (N-CNFs) and amorphous microporous carbon materials (N-AMCMs). It was found that the above characteristics can be regulated by varying synthesis conditions: precursor compositions and reaction temperature and time. Mesoporous nitrogencontaining CNFs with a specific surface area of 30–350 m2/g and a pore volume of 0.10–0.83 cm3/g were formed by the catalytic decomposition of a mixture of ethylene with ammonia at 450–675°C. Microporous materials (N-AMCMs) with a specific surface area of 472–3436 m2/g and a micropore volume of 0.22–1.88 cm3/g were prepared by the carbonization of nitrogen-containing organic compounds at 700–900°C. An increase in the carbonization temperature and reaction time resulted in an increase in the specific surface area and microporosity of N-AMCMs, whereas lower temperatures of 450–550°C and reaction times of 1–3 h were optimal for the preparation of N-CNFs with a developed texture. It was found that milder synthesis conditions and higher nitrogen contents of precursors were required for obtaining high nitrogen concentrations in both N-CNFs and N-AMCMs. The synthetic method developed allowed to prepare carbon supports with nitrogen contents up to 8 wt %.
SYNTHESIS OF NITROGEN-CONTAINING CARBON NANOFIBERS BY CATALYTIC DECOMPOSITION OF ETHYLENE/AMMONIA MIXTURE
A.E. Shalagina, Z.R. Ismagilov, O.Yu. Podyacheva, R.I. Kvon, V.A. Ushakov
Carbon, 45(9) (2007) pp. 1808-1820.
The formation of carbon nanofibers (CNFs) doped with nitrogen was investigated during decomposition of C2H4/NH3 mixtures at 450–675°C over metal catalysts: 90Ni–Al2O3, 82Ni–8Cu–Al2O3, 65Ni–25Cu–Al2O3, 45Ni–45Cu–Al2O3, 90Fe–Al2O3, 85Fe–5Co–Al2O3, 62Fe–8Co–Al2O3, 62Fe–8Ni–Al2O3. It was found that the yield of CNFs, their structural and textural properties, as well as nitrogen content in CNFs are strongly dependent on the synthesis conditions such as: catalyst used, feed composition, temperature and duration. The 65Ni–25Cu–Al2O3 was proved to be the most efficient catalyst for the production of nitrogen-containing carbon nanofibers (N-CNFs) with nitrogen content up to 7 wt.%. Ammonia concentration in the feed equal 75 vol.%, temperature 550°C and duration 1 h were found to be the optimum reaction parameters to reach the maximum nitrogen content in N-CNFs. TEM studies revealed that the nanofibers have a helical morphology and a “herringbone” structure composed of graphite sheets. According to the XPS data, the nitrogen incorporation in the N-CNF structure leads to the formation of two types of nitrogen coordination: pyridinic and quaternary, and their abundance depends on the reaction conditions.
NOVEL CARBON NANOFIBERS WITH Ni-Mo AND Co-Mo NANOPARTICLES FOR HYDRODESULFURIZATION OF FUELS
Z.R. Ismagilov, A.E. Shalagina, O.Yu. Podyacheva, V.A. Ushakov, V.V. Kriventsov, D.I. Kochubey, A.N. Startsev
Intern. Sci. J. Alternative Energy Ecology, 3(47) (2007) pp. 150-158.
Methane decomposition over Ni–Mo–Al2O3 (10 wt. % Al2O3) and Co–Mo–Al2O3 (25 wt. % Al2O3) catalysts was studied at 550 and 500°C. TEM, EDX and XRD investigations revealed localization of parent metal catalyst nanoparticles on the tips of the resulting carbon nanofibers (CNFs). The composition of these particles and the state of Ni, Co and Mo were examined by EXAFS spectroscopy. The catalytic activity of the isolated Ni–Mo and Co–Mo nanoparticles located on the tips of separate CNFs was tested in thiophene hydrodesulfurization (HDS) at 300°C. The HDS activities of the CNF catalysts were found to be comparable with those of highly dispersed bimetallic sulfide catalysts supported on Sibunit carbon.
PREPARATION AND INVESTIGATION OF NANOSTRUCTURED CARBONACEOUS COMPOSITES FROM THE HIGH-ASH BIOMASS
V.A. Yakovlev, P.M. Yeletsky, M.Yu. Lebedev, D.Yu. Ermakov, V.N. Parmon
Chem. Eng. J., 134(1-3) (2007) pp. 246-255.
The various pathways of high-ash biomass processing to the valuable carbonaceous composites are considered. From the rice husk carbon–silica composites and supermicroporous carbon materials (SMC) were prepared. In the new SMCs, the specific surface area ABET reaches 3460 m2/g while micropore volume Vμ is up to 1.9 cm3/g at the total of pore volume, VΣ, as large as 3.0 cm3/g. These carbons were shown to absorb up to 41 wt% of methane at room temperature and 60 atm and more than 6 wt% of hydrogen under mild cryogenic conditions (at 77 K). Also methods for the synthesis of carbon– silica composites with ABET up to 710 m2/g and with average size of SiO2 particles less 5 nm are proposed. The expected practical application of the obtained carbon–silica composites may be first of all reinforcing rubber extenders and bi-functional sorbents for the gas and liquid purification.
CARBON ADSORBENTS AS HYDROGEN FUEL STORAGE MEDIA FOR VEHICULAR APPLICATIONS
V.B. Fenelonov, E.A. Ustinov*, V.A. Yakovlev, Ch.N. Barnakov*, M.S. Melgunov (*NPO Provita, St. Petersburg, Russia; **Institute of Coal and Coal Chemistry, Kemerovo, Russia)
Kinet. Catal., 48(4) (2007) pp. 599-602.
The prospects of carbon adsorbents as vehicular hydrogen storage media are briefly discussed.
NANOSCALE CARBON FORMATION FROM VARIOUS HYDROCARBONS OVER NANOCRYSTALLINE Co/MgO CATALYST
V.V. Chesnokov, V.I. Zaikovskii, I.E. Soshnikov
J. Phys. Chem. C, 111(22) (2007) pp. 7868-7874.
A series of nanocrystalline MgO samples containing 1.2-15.9% carbon were prepared by MgO carbonization at 500°C in 1,3-butadiene flow diluted with argon in a 1:75 ratio. For the sample with 15.9% C almost all the MgO surface was covered with carbon. An increase of the MgO carbonization rate from 500 to 750°C resulted in the growth of the carbon deposition rate. Still, the carbon deposits covered the MgO surface in a fairly uniform way. This is proved by the very high surface area (2000-2500 m2/g) of porous carbon obtained by dissolving MgO from the carbonized samples with hydrochloric acid. Nanocrystalline MgO was used as a support for synthesis of Co/MgO catalysts. The concentration of supported cobalt was varied from 2.5 to 30%. The nature and formation kinetics of carbon deposits from butadiene over Co/MgO catalysts were studied. Highresolution transmission electron microscopic (HRTEM) studies showed that carbonization of the Co/MgO catalyst in butadiene diluted with argon in the temperature range of 600-750°C resulted in the formation of carbon nanotubes and a carbon film decorating the MgO surface. Unlike butadiene, methane was not found to carbonize the MgO surface at temperatures below 800°C. Carbonization of the Co/MgO catalysts with methane in the temperature range of 600-800°C resulted in the formation of carbon nanotubes. As reduction of the catalysts with hydrogen was found to yield highly dispersed cobalt nanoparticles with a narrow particle size distribution, the resulting carbon nanotubes are characterized by high uniformity. The number of layers in the nanotubes varied from one layer to six to eight layers depending on the reduction conditions and carbonization temperature. In the case of methane, a carbonization temperature increase from 600 to 800°C led to a decrease of the carbon nanotube diameter from 4-5 to 1-2 nm and the number of layers from one to three layers to one layer. The observed decrease of the nanotube diameter with the temperature increase was explained assuming the key role of the graphite phase nuclei in the formation of carbon nanotubes.
PREPARATION AND CHARACTERIZATION OF ALUMINOSILICATE SUPPORTS WITH A SYNTHESIZED LAYER OF CATALYTIC FILAMENTOUS CARBON. I. SYNTHESIS OF CARBON NANOFIBERS ON A SUPPORTED NICKEL CATALYSTG.A. Kovalenko, O.V. Komova, T.V. Chuenko, N.A. Rudina, L.V. Perminova
Kinet. Catal., 48(5) (2007) pp. 749-756.
The synthesis of catalytic filamentous carbon (CFC) on a Ni catalyst supported by homogeneous precipitation onto the surface of aluminosilicate ceramic supports (honeycomb monoliths, ceramic foam, glass foam, and haydite) was studied. The effects of CFC synthesis conditions (the catalyst concentration on a support, the pyrolysis temperature of a propane–butane mixture, and the composition of the gas mixture) on the specific surface areas of supports, the yield of carbon, and the morphology of a surface CFC layer were examined. As found by scanning electron microscopy, the uniformity of distribution and the size of carbon nanofibers synthesized depended on the conditions of their synthesis. The resulting CFC-containing supports were tested as adsorbents for the immobilization of enzymatically active substances (individual enzymes, cell membranes, and microorganisms) in order to prepare highly stable heterogeneous catalysts for biotechnology and biocatalysis.
PREPARATION AND CHARACTERIZATION OF ALUMINOSILICATE SUPPORTS WITH A SYNTHESIZED LAYER OF CATALYTIC FILAMENTOUS CARBON. II. SYNTHESIS OF CARBON NANOFIBERS ON A SUPPORTED COBALT CATALYST
G.A. Kovalenko, N.A. Rudina, T.V. Chuenko, L.V. Perminova, T.G. Terentieva, A.S. Rozanov*, S.N. Zagrebel’nyi* (*Novosibirsk State University, Novosibirsk, Russia)
Kinet. Catal., 48(5) (2007) pp. 757-764.
The synthesis of a layer of catalytic filamentous carbon (CFC) on a Co catalyst supported by homogeneous precipitation onto the surface of aluminosilicate supports (ceramic foam and vermiculite) was studied. The effects of CFC layer synthesis conditions (the catalyst concentration on a support, the pyrolysis temperature of a propane– butane mixture, and the composition of the gas mixture) on the specific surface areas of supports, the yield of carbon ((g C)/(g Co)), and the morphology of a surface CFC layer were examined. It was found that, in the case of ceramic foam, the concentration of cobalt hydroxide precipitated on the surface was lower by a factor of 15 and the yield of carbon was higher by a factor of 20–40 than those in vermiculite. The specific surface areas of supports, the yield of carbon, and the amount of synthesized carbon increased as the pyrolysis temperature of a propane–butane mixture was increased from 500 to 600°C. As found by scanning electron microscopy, the carbon content increased with pyrolysis temperature because of an increase in the length of carbon nanofibers. The properties (activity and stability) of biocatalysts prepared by the adsorption immobilization of a recombinant protein having glucose isomerase activity on CFC–Co-containing supports (ceramic foam and vermiculite) were studied.
CATALYTIC PROPERTIES OF GLUCOAMYLASE IMMOBILIZED ON SYNTHETIC CARBON MATERIAL SIBUNIT
G.A. Kovalenko, L.V. Perminova, T.G. Terentieva, G.V. Plaksin* (*Institute of Hydrocarbon Processing, Omsk, Russia)
Appl. Biochem. Microbiol., 43(4) (2007) pp. 374-378.
Glucoamylase (commercial preparation Glucavamorin) was immobilized by sorption on a carbon support Sibunit. Starch saccharification by the resulting biocatalyst (dextrin hydrolysis) was studied. Investigation of the effect of adsorptional immobilization on kinetic parameters of glucoamylase, including the rate constant of thermal inactivation, showed that immobilization of Glucavamorin on Sibunit resulted in a thousand fold increase in glucoamylase stability in comparison with the dissolved enzyme. Presence of the substrate (dextrins) in the reaction mixture had a considerable stabilizing effect. Increase in dextrin concentration increases the thermostability of the immobilized enzyme. The overall factor of glucoamylase stabilization adsorbed on Sibunit with the presence of 53% dextrin solutions in comparison with the dissolved enzyme approximated 105. The biocatalyst for starch saccharification made on the base of Subunit-adsorbed Glucavamorin had a high operational stability. Its half-inactivation time at 60°C exceeded 30 days.
SYNTHESIS OF MULTIWALL CARBON NANOTUBES OVER COBALT CATALYSTS
N.N. Yuferev*, S.N. Blinov*, S.G. Zavarukhin, A.A. Timofeev*, E.V. Rakova*, E.G. Rakov* (*Mendeleev University of Chemical Technology; Shubnikov Institute of Crystallography; Moscow Engineering Physical Institute, Moscow, Russia)
Theor. Found. Chem. Eng., 41(5) (2007) pp. 634-638.
CH4 pyrolysis over Co/Al2O3 (60 wt %) catalysts, prepared by different methods and doped with tervalent-metal oxides, was studied gravimetrically under isothermal conditions at 600–750°C and the atmospheric pressure. The process starts at the maximum rate and decays with time. The pyrolysis rate is a function of linear CH4 rate peaks at 40 cm/min. With the provision of the maximum process rate, the activation energy of CH4 pyrolysis over various catalysts falls within a range of 150–240 kJ/mol. For catalysts with identical compositions, the activity depends on their preparation. Transmission electron microscopy showed that the product was multiwall carbon nanotubes with diameters ranging from 6 to 30 nm. Mathematical equations were proposed to describe the process kinetics. A productivity of 12 g/h is achieved on a laboratory continuous reactor.
FORMATION OF A NICKEL CATALYST ON THE SURFACE OF ALUMINOSILICATE SUPPORTS FOR THE SYNTHESIS OF CATALYTIC FIBROUS CARBON
O.V. Komova, A.V. Simakov, G.A. Kovalenko, N.A. Rudina, T.V. Chuenko, N.A. Kulikovskaya
Kinet. Catal., 48(6) (2007) pp. 803-811.
Conditions for the homogeneous precipitation of nickel hydroxide in the presence of urea onto the surface of aluminosilicate honeycomb monoliths, which were prepared based on clay, talc, and amorphous aluminum hydroxide, were examined. Factors affecting the concentration of supported nickel (synthesis time, starting solution concentrations, loaded amount of the support, and support calcination temperature) were studied. The possibility of supporting nickel hydroxide onto the surface of cellular ceramic foam, glass foam, and haydite was demonstrated. The morphology of nickel hydroxide particles, nickel metal particles on support surfaces, and carbon coatings synthesized in the course of the catalytic pyrolysis of a propane–butane mixture was studied by scanning electron microscopy.
MODELING OF HETEROGENEOUS SURFACES AND CHARACTERIZATION OF POROUS MATERIALS BY EXTENDING DENSITY FUNCTIONAL THEORY FOR THE CASE OF AMORPHOUS SOLIDS
E.A. Ustinov*, D.D. Do**, V.B. Fenelonov (*NPO Provita, St. Petersburg, Russia; **University Queensland, St Lucia, Australia)
Appl. Surf. Sci., 253(13) (2007) pp. 5610-5615.
A method of characterization of carbonaceous materials using nongraphitized carbon black as a reference is considered. The Tarazona density functional theory was applied to amorphous solids to describe nitrogen adsorption on nongraphitized carbon black. This allows to describe energetic heterogeneity without the need to invoke any energy distribution functions. To derive the pore size distribution (PSD) of porous carbon whose pore walls are nongraphitized, the entropy concept in the regularization method was used. With this approach PSD is more well-behaved than that obtained with the usual means. This new theory was applied to study the effects of technological parameters on porous structure of a series of activated carbon.
CHARACTERIZATION OF THE POROUS STRUCTURE OF CARBON MATERIALS BY MEANS OF DENSITY FUNCTIONAL THEORY
E.A. Ustinov*, V.B. Fenelonov, V.A. Yakovlev, P.I. Eletskii* (*NPO Provita, St. Petersburg, Russia)
Kinet. Catal., 48(4) (2007) pp. 589-598.
Nitrogen adsorption isotherms were analyzed using density functional theory (DFT) to characterize active carbons. It is shown how the effect of technological parameters on the structure of active carbons can be revealed with the help of DFT. DFT is used to analyze the pore-size distribution and to determine the pore surface area for active carbons of different types.
PROPERTIES OF A GLASS SURFACE MODIFIED BY A NEW FROSTING PASTE. SURFACE MORPHOLOGY
O.N. Sidelnikova*, A.N. Salanov (*Institute of the Chemistry of Solids, Moscow, Russia)
Glass Ceramics, 64(11-12) (2007) pp. 425-428.
A new paste is proposed for frosting glass surfaces. The action of the paste is based on the physical-chemical process of surface chemical ion exchange. The paste does not contain hydrofluoric acid or its derivatives. The frosting process occurs at 300°C and differs substantially from the existing frosting processes — chemical etching and sandblasting. Electron microscope investigations of the glass surface were performed with a JSM-6460RV scanning electron microscope (Jeol, Japan). The morphology of the surface layer of the frosted glass is characterized by a system of microblocks (linear dimensions 50–150 μm) and microcracks (width 100– 200 nm). The microblocks have even faces and a smooth frontal surface. The surface morphology of the glass is the same after frosting and subsequent deposition of a metal by chemical reduction.
NEW FAMILY OF MATERIALS FOR ADSORPTION COOLING: MATERIAL SCIENTIST APPROACH
Yu.I. Aristov
J. Eng. Thermophys., 16(2) (2007) pp. 63-72.
This paper summarises literature data concerning a new family of materials for adsorptive cooling. They are composites of a type “a salt confined to a porous host matrix” (so called Selective Water Sorbents or SWSs). These materials demonstrate an intermediate behaviour between solid adsorbents, salt hydrates and liquid absorbents. Thermodynamic equilibrium with water vapour has been measured for more than thirty SWSs based on halides, sulphates and nitrates of alkaline and alkaline earth metals, that are confined to various matrices (silica, alumina, porous carbons, clays, MCM-41, etc.). The important advantage of the SWSs is the possibility to controllably modify their water sorption properties in a wide range by varying a) chemical nature of the impregnated salt, b) porous structure of the host matrix, c) the amount of the confined salt, and d) preparation conditions. This, in principle, allows purposeful synthesis of new solid sorbents with predetermined properties which fit demands of particular adsorptive cycle. Appropriate examples are presented in the paper. Recent study of adsorption chillers with granulated and compact layers of SWS-1L (CaCl2 in mesoporous silica) showed the experimental COP as high as 0.6 that is larger than reported for “silica gel/water” and “zeolite/water” systems at the same cycle conditions. The concept of matrix modification with an active salt can be also used for synthesis of efficient sorbents of carbon dioxide, methanol and ammonia. Other practical applications of SWSs are briefly discussed, such as heat protection, gas drying and fresh water production from the atmosphere.
NOVEL MATERIALS FOR ADSORPTIVE HEAT PUMPING AND STORAGE: SCREENING AND NANOTAILORING OF SORPTION PROPERTIES
Yu.I. Aristov
J. Chem. Eng. Japan, 40(13) (2007) pp. 1241-1251.
The brief review of innovative materials for adsorptive pumping and storage of low temperature heat as well as current trends in this field showed their great potential. To implement it in the near future it is reasonable to follow two complementary lines: (a) systematic testing for this application novel adsorbents initially developed for other targets (gas drying, separation, etc.), and (b) tailoring of new specific porous materials adapted just to variety of adsorptive cooling, heating and storage cycles under different climatic and boundary conditions. The main idea of the latter approach is that for each particular adsorptive cycle there is an optimal adsorbent, the thermodynamic characteristics of which could allow perfect performance of this cycle. The first step of the analysis is the formulation of requirements to this desirable (ideal) adsorbent. Then, the final step is to design and synthesize a new adsorbent with sorption properties close or even equal to those determined before as perfectly fitting the cycle. Particular examples of nanotailoring of adsorption properties are given for two phase materials, composites “a salt in a porous host matrix”, which can be used as efficient adsorbents of water, methanol and ammonia.
AN ADVANCED SOLID SORPTION CHILLER USING SWS-1L
A. Freni*, F. Russo*, S. Vasta*, M.M. Tokarev, Yu.I. Aristov, G. Restuccia* (*ITAE CNR, Messina, Italy)
Appl. Therm. Eng., 27(13) (2007) pp. 2200-2204.
In this paper, the experimental testing on an advanced solid sorption chiller based on a heat exchanger coated with a compact layer of SWS-1L (CaCl2 in mesoporous silica gel) is presented. The experimental results showed a specific power of 150-200 W/kg of adsorbent and a cycle time of 10-20 minutes. These values are sensibly better (i.e. one order of magnitude different) than those measured in the same unit working with a SWS-1L pelletised bed. The cooling COP ranged between 0.15 and 0.3, depending on the operating conditions.
SOLAR DRIVEN ADSORPTIVE CHILLER: AT THE INTERFACES BETWEEN CHEMICAL AND THERMAL ENGINEERING
Yu.I. Aristov, D. Chalaev*, B. Dawoud**, L.I. Heifets**, O. Popel***, G. Restuccia**** (*Institute of Engineering Thermal Physics, Kiev, Ukraine; **Moscow Lomonosov State University, Moscow, Russia; ***Joint Institute for High Temperatures, Moscow, Russia; ****ITAE CNR, Messina, Italy)
Chem. Eng. J., 134(1-3) (2007) pp. 58-65.
Thermochemical systems for energy conversion are just at the interface between chemical and thermal engineering because the final aim is a transformation of energy, while the specific tool is a thermally driven chemical reaction. Designing the efficient systems calls for appropriate choice of chemical process, comprehensive analysis of its thermodynamics and kinetics, intensification of heat and mass transfer, intelligent integration of components into overall heat device, etc. This paper reviews the joint activity of the six Institutes from the four countries on applying chemical reactions in modern devices for production of cold, which are driven by solar heat.
SORPTION EQUILIBRIUM OF METHANOL ON NEW COMPOSITE SORBENT «CaCl2/Silica Gel»
Yu.I. Aristov, L.G. Gordeeva, Yu.D. Pankratiev, L.M. Plyasova, I.V. Bikova, A. Freni*, G. Restuccia* (*ITAE CNR, Messina, Italy)
Adsorption, 13(2) (2007) pp. 121-127.
This paper presents experimental data on methanol sorption on new composite sorbents which consist of mesoporous silica gels and calcium chloride confined to their pores. Sorption isobars and XRD analysis showed the formation of a solid crystalline solvate CaCl2·2MeOH at low methanol uptake, while at higher uptake the formation of the CaCl2-methanol solution occurred. The solution confined to the silica pores showed the sorption properties similar to those of the CaCl2-methanol bulk solution. Calorimetric and isosteric analyses showed that the heat of methanol sorption depends on the methanol uptake, ranging from 38±2 kJ/mol for the solution to 81±4 kJ/mol for the solid crystalline phase CaCl2·2MeOH. The above mentioned characterizations allowed the evaluation of the methanol sorption and the energy storage capacities, clearly showing that the optimal applications of these new composite sorbents are the methanol removal from gaseous mixtures, heat storage and sorption cooling driven by low temperature heat.
MODELING OF THE LIMITING STEP OF WATER SORPTION BY COMPOSITE SORBENTS OF THE “CALCIUM CHLORIDE IN POROUS MATRIX” TYPE
N.M. Ostrovskii*, N.A. Chumakova, N.M. Bukhavtsova*, N.V. Vernikovskaya, Yu.I. Aristov (*Institute of Hydrocarbons Processing, Omsk, Russia)
Theor. Found. Chem. Eng., 41(1) (2007) pp. 83-90.
A nonstationary model is proposed to describe the water sorption from air by composite sorbents of the “salt in a porous matrix” type via the interaction of water with the salt to form a salt solution in pores. It is shown that the dynamics of the moisture content at the adsorber outlet cannot be described under the assumption of constancy of the effective sorption rate constant. The limiting step of water sorption is analyzed, and it is supposed that the limiting step is the water diffusion through the solution layer forming near the external surface of a granule. An expression for the sorption rate constant as a function of the moisture content of the sorbent is proposed that takes into account the monotonic decrease in this constant with an increase in the amount of water sorbed. The effective diffusion coefficient at the limiting step of sorption is determined, which turns out to be close to the effective diffusion coefficient in an aqueous calcium chloride solution.
EFFECT OF CAPILLARY CONDENSATION ON WATER SORPTION BY COMPOSITE CALCIUM CHLORIDE IN A POROUS MATRIX SORBENTS
N.M. Ostrovskii*, N.A. Chumakova, N.M. Bukhavtsova*, N.V. Vernikovskaya, Yu.I. Aristov (*Institute of Hydrocarbons Processing, Omsk, Russia)
Theor. Found. Chem. Eng., 41(2) (2007) pp. 200-204.
To develop a model of water sorption from air by composite salt in a porous matrix sorbents, the effect of capillary condensation was studied. It was shown that, at high humidity of incoming air, it is necessary to take into account the capillary condensation of water in small pores of the matrix because the capillary condensation significantly affects the concentration and temperature profiles in the sorbent bed and leads to intense moisture accumulation at the bed inlet. The model was used to study the kinetics of water vapor sorption in a flow adsorber with a fixed bed of calcium chloride in porous aluminum oxide and calcium chloride in a porous carbon–carbon composite Sibunit sorbents.
ADSORPTIVE AIR CONDITIONING SYSTEMS DRIVEN BY LOW TEMPERATURE ENERGY SOURCES: CHOICE OF WORKING PAIRS
L.G. Gordeeva, A. Freni*, G. Restuccia*, Yu.I. Aristov (*CNR-Istituto di Technologie Avanzate per l’Energia)
J. Chem. Eng. Japan, 40(13) (2007) pp. 1287-1291.
The performance of an adsorptive air-conditioning cycle driven by low temperature heat (80–85°C) was studied. The analysis rested on the Polanyi potential theory and took into account literature and author’s experimental data on sorption equilibrium of various conventional and innovative adsorbents with water and methanol as working fluids. This adsorbent screening is aimed at evaluating the optimal working pairs for this application. The composite sorbent of methanol Lithium Chloride in mesoporous silica gel and the adsorbent of water FAM-Z02 were selected as challenging pairs for severe conditions of heat rejection typical for solar cooling in hot countries and air conditioning in cars.
INFLUENCE OF CHARACTERISTICS OF METHANOL SORBENTS “SALTS IN MESOPOROUS SILICA” ON THE PERFORMANCE OF ADSORPTIVE AIR CONDITIONING CYCLE
L.G. Gordeeva, A. Freni*, G. Restuccia*, Yu.I. Aristov (*ITAE CNR, Messina, Italy)
Ind. Eng. Chem. Res., 46(9) (2007) pp. 2747-2752.
In this paper a new family of methanol sorbents “salts in mesoporous silica” is proposed for utilization in an adsorptive air conditioner driven by a lowtemperature heat (T = 338-373 K). The methanol sorption capacity of composites, under typical cooling cycle conditions, was measured by an express method based on the Polanyi principle of temperature invariance. An estimation of the cooling coefficient of performance (COP) was carried out in order to compare the performance of such sorbents with other methanol and water sorbents. Results obtained showed that most of the synthesized composites present methanol sorption ability higher than that of common methanol sorbents (e.g., active carbons). The composite LiCl (30.6 wt %)/SiO2 shows the highest sorption capacity, wads = 0.8 g/g, and uptake variation per cycle, Δw = 0.71 g/g. The corresponding cooling COP is 0.74 (maximum Tdes = 363 K, single-bed cycle), which is comparable to typical COP values for the best water sorbents.
ISOTHERMAL SORPTION CHARACTERISTICS OF THE BaCl2–NH3 PAIR IN A VERMICULITE HOST MATRIX
Y. Zhong*, R.E. Critoph*, R.N. Thorpe*,Z. Tamainot-Telto*, Yu.I. Aristov (*Warwick University, UK)
Appl. Therm. Eng., 27(14-15) (2007) pp. 2455-2462.
Chemisorption could be useful in adsorption systems due to the large concentration change compared with physisorption. Equilibrium concentration characteristics of ammonia with a composite adsorbent material (BaCl2 impregnated into a vermiculite matrix) are investigated: the maximum concentration is about 0.4 kg ammonia/ kg adsorbent. Hysteresis was observed between the synthesis and the decomposition reaction. The analysis of the data suggests that the hysteresis could be due to the dimensional changes of the solid during the reactions. The bivariant behaviour observed was contrary to the monovariant behaviour anticipated and the reasons are discussed. The COP of a basic adsorption cycle for typical ice-making and airconditioning applications utilizing ammonia and the composite material were calculated. The results show that the material could be used for air conditioning or other refrigeration applications. The COP could reach up to 0.6 at typical conditions (Tev=15°C, Tcon=35 °C).
A NEW APPROACH TO REGENERATING HEAT AND MOISTURE IN VENTILATION SYSTEMS
Yu.I. Aristov, I.V. Mezentsev*, V.A. Mukhin* (*Institute of Thermal Physics, Novosibirsk, Russia)
Energy and Buildings, 40(3) (2008) pp. 204-208.
For countries with a cold climate the large difference (30-60°C) in winter between indoor and outdoor temperatures leads to a) large heat losses in ventilation systems; b) moisture freezing at the systems exit and c) great reduction in the indoor humidity. Here a new approach is presented for regenerating heat and moisture in ventilation systems in cold climates which allows resolution of these problems. The method has been tested under climatic conditions of West Siberia (winter 2005-2006). The prototype system requires very little maintenance, has a low capital cost, is compact and energy efficient. Technical, economic and social aspects of this method are discussed.
CHANGE OF CO2 CARRYING CAPACITY OF CaO IN ISOTHERMAL RECARBONATIONDECOMPOSITION CYCLES
A.I. Lysikov, A.N. Salanov, A.G. Okunev
Ind. Eng. Chem. Res., 46(13) (2007) pp. 4633-4638.
The change of CO2 carrying capacity of CaO sorbents prepared from different precursors has been studied using thermogravimetric analysis in a long series of isothermal recarbonation-decomposition cycles in the temperature range of 750-850°C. The residual capacity of the CaO sorbents after a large number of cycles was found to depend on the precursor type, the experimental temperature, and the duration of the recarbonation stage. The residual capacities of the CaO derived from the powdered calcium carbonates were much higher than that of the CaO produced from the crystalline CaCO3. A simple tentative model has been suggested, according to which recarbonation-decomposition cycles result in formation of the interconnected CaO network that acts as a refractory support and determines sorption properties of the material. By using a new model, a simple synthesis procedure has been suggested that produces CaO sorbents with high residual CO2 carrying capacities
ON THE INFLUENCE OF THE METAL LOADING ON THE STRUCTURE OF CARBONSUPPORTED PTRU CATALYSTS AND THEIR ELECTROCATALYTIC ACTIVITIES IN CO AND METHANOL ELECTROOXIDATION
A.N. Gavrilov*, E.R. Savinova, P.A. Simonov, Institute of Thermal Physics, Novosibirsk, Russia) V.I. Zaikovskii, S.V. Cherepanova, G.A. Tsirlina*, V.N. Parmon (*Moscow Lomonosov State University, Moscow, Russia)
Phys. Chem. Chem. Phys., 9(40) (2007) pp. 5476-5489.
PtRu (1 : 1) catalysts supported on low surface area carbon of the Sibunit family (SBET = 72 m2 g–1) with a metal percentage ranging from 5 to 60% are prepared and tested in a CO monolayer and for methanol oxidation in H2SO4 electrolyte. At low metal percentage small (<2 nm) alloy nanoparticles, uniformly distributed on the carbon surface, are formed. As the amount of metal per unit surface area of carbon increases, particles start coalescing and form first quasi two-dimensional, and then threedimensional metal nanostructures. This results in a strong enhancement of specific catalytic activity in methanol oxidation and a decrease of the overpotential for CO monolayer oxidation. It is suggested that intergrain boundaries connecting crystalline domains in nanostructured PtRu catalysts produced at high metal-on-carbon loadings provide active sites for electrocatalytic processes.
THERMAL CONDUCTIVITY OF COMPOSITE CATALYSTS CONTAINING METALLIC COPPER AS A REINFORCING COMPONENT
S.V. Dimov*, A.G. Sipatrov, N.A. Rudina, V.V. Kuznetsov*, A.A. Khassin (*Kutateladze A.N. Gavrilov*, E.R. Savinova, P.A. Simonov, Institute of Thermal Physics, Novosibirsk, Russia) V.I. Zaikovskii, S.V. Cherepanova, G.A. Tsirlina*, V.N. Parmon (*Moscow Lomonosov State University, Moscow, Russia)
Theor. Found. Chem. Eng., 41(2) (2007) pp. 184-192.
The dependences of the electrical and thermal conductivities of porous composite materials containing a metallic component (copper) on the volume copper content are investigated experimentally. The measured thermal conductivities of samples prepared according to the proposed technique indicate that the thermal conductivity of monolithic catalysts with a copper content of no less than 15 vol % exceeds 1 W m–1 K–1. This corresponds to the formation of a connected cluster consisting of conducting spheres in a random packing of conducting and insulating spheres. A comparative analysis of the thermal and electrical conductivities of the composites demonstrates that, at a copper content of higher than 20 vol %, the thermal conduction through a percolation cluster formed by copper particles makes the dominant contribution. In employing composite materials containing a catalytically active component in exothermic catalytic processes (Fischer–Tropsch synthesis, steam conversion of carbon monoxide CO, etc.), their high thermal conductivity is an important advantage that makes it possible to decrease the temperature gradient across the porous composite catalyst bed. A semiempirical method for calculating the thermal conductivity of composites is developed. The results of the calculations performed using the proposed method are in good agreement with experimental data.
MODEL Pd-BASED BIMETALLIC SUPPORTED CATALYSTS FOR NITRATE ELECTROREDUCTION
S.N. Pronkin, P.A. Simonov, V.I. Zaikovskii, E.R. Savinova
J. Mol. Catal. A: Chem., 265(1-2) (2007) pp. 141-147.
An approach for in situ preparation of bimetallic Pd–Cu catalysts active in nitrate electroreduction is described. The catalysts are prepared by modification of the surface of Pd carbon-supported nanoparticles by monolayer of Cu. The morphology of Pd/C nanoparticles is characterized by HR-TEM and by their electrochemical properties in the adsorption of hydrogen and Cu adatoms. Modification of Pd surface by Cu adlayer results in significant increase of the activity in nitrate electroreduction. Dependencies of the reaction rate for Cu/Pd/C catalysts on the electrode potential, nitrate concentration and anion of supporting electrolyte are discussed.
ELECTRICAL PROPERTIES OF NANOCOMPOSITES BASED ON COMB-SHAPED NEMATIC POLYMER AND SILVER NANOPARTICLES
N.A. Nikonorova*, E.B. Barmatov**, D.A. Pebalk***, M.V. Barmatova, G. Domínguez-Espinosa****, R. Diaz-Calleja****, P. Pissis***** (*Institute of Macromolecular Compounds, St. Petersburg, Russia; **Novosibirsk Technological Center Shlumberger, Novosibirsk, Russia; ***Moscow Lomonosov State University, Moscow, Russia; ****Polytechnic University of Valencia, Valencia, Spain; *****National Technical University of Athens, Athens, Greece)
J. Phys. Chem. C, 111(24) (2007) pp. 8451-8458.
A nematic comb-shaped copolymer and its nanocomposites containing 0.063-0.54 in vol % of silver nanoparticles were studied by broadband dielectric spectroscopy. The frequency dependence of specific alternating current (ac) conductivity was used to estimate the temperature-frequency intervals of charge transfer by long and short distances, respectively. With increasing the concentration of nanoparticles, specific ac conductivity increases. The concentration dependence of dielectric permittivity suggests that distribution of nanoparticles is homogeneous, and conducting channels are not formed. With increasing the concentration of silver nanoparticles, the glass transition temperature of the nanocomposites, described in terms of the strength/fragility concept, increases, whereas the strength parameter D decreases (i.e., "fragility" increases).
INFLUENCE OF CARBON SUPPORT ON THE PERFORMANCE OF PLATINUM BASED OXYGEN REDUCTION CATALYSTS IN A POLYMER ELECTROLYTE FUEL CELL
J. Kaiser*,**, P.A. Simonov, V.I. Zaikovskii, Ch. Hartnig*, L. Jörissen*, E.R. Savinova (*Center for Solar Energy and Hydrogen Research, Ulm, Germany; **Degussa-Initiators GmbH & Co. KG, Pullach, Germany)
J. Appl. Electrochem., 37(12) (2007) pp. 1429-1437.
Novel carbons from the Sibunit family prepared via pyrolysis of hydrocarbons [Yermakov YI, Surovikin VF, Plaksin GV, Semikolenov VA, Likholobov VA, Chuvilin AL, Bogdanov SV (1987) React Kinet Catal Lett 33:435] possess a number of attractive properties for fuel cell applications. In this work Sibunit carbons with BET surface areas ranging from ca. 20 to 420 m2 g−1 were used as supports for platinum and the obtained catalysts were tested as cathodes in a polymer electrolyte fuel cell. The metal loading per unit surface area of carbon support was kept constant in order to maintain similar metal dispersions (~0.3). Full cell tests revealed a strong influence of the carbon support texture on cell performance. The highest mass specific activities at 0.85 V were achieved for the 40 and 30 wt.% Pt catalysts prepared on the basis of Sibunit carbons with BET surface areas of 415 and 292 m2 g−1. These exceeded the mass specific activities of conventional 20 wt.% Pt/Vulcan XC-72 catalyst by a factor of ca. 4 in oxygen and 6 in air feed. Analysis of the I–U curves revealed that the improved cell performance was related to the improved mass transport in the cathode layers. The mass transport overvoltages were found to depend strongly on the specific surface area and the texture of the support
.STABILIZATION OF PALLADIUM IN HOMOGENEOUS CHLORIDELESS CATALYSTS FOR OLEFINS C2-C4 OXIDATION INTO CARBONYL COMPOUNDS WITH OXYGEN
V.F. Odyakov, E.G. Zhizhina, K.I. Matveev
Catal. Ind., 4 (2007) pp. 19-25.
The first step of homogeneous oxidation of olefins C2-C4 by dioxygen in the presence of catalyst Pd + HPA-x, where HPA-x is molybdovanadophosphoric heteropoly acid H3+xPVV xMo12-xO40, is reduction of HPA-x with olefin in the presence of Pd complexes into HmHPA-x at 30– 60°C. Here m = [VIV]Σ / [HPA-x] is a degree of reduction of the catalyst. In this case, the redoxsystem Pd 1 2/Pd02 works, but it converts into Pd2+/Pdmet system with higher redox potential with increasing of temperature. During this transformation, interval of m values where the catalyst remains homogeneous diminishes, and metallic Pd begins to precipitate from the reduced catalyst. To prevent Pd precipitation, it is necessary to introduce stabilizers of Pd. As stabilizers, 2,6-pyridinecarboxylic (dipicolinic) acid (I) and cheaper 3-pyridinesulfonic acid are proposed. In the presence of these stabilizers, activity of the catalyst diminishes, but an area of its homogeneity expands. Complexes of Pd with I are stable at temperatures of regeneration of the catalyst (150–160°C). Therefore, I is considered as rather perspective stabilizer of Pd in catalysts Pd + HPA-x and can be used in industrial homogeneous processes of olefins C2–C4 oxidation by oxygen.
STABILITY OF PALLADIUM IN HOMOGENEOUS CHLORIDE-FREE CATALYSTS Pd + HETEROPOLY ACID FOR OXIDATION OF C2-C4 ALKENES BY DIOXYGEN
E.G. Zhizhina, V.F. Odyakov, K.I. Matveev
React. Kinet. Catal. Lett., 91(2) (2007) pp. 325-332.
A possibility of the use of polycarboxylic acids as stabilizers of Pd in homogeneous catalysts for the oxidation of C2–C4 alkenes is studied. Pyromellitic acid is shown to have the stabilizing properties.
HOMOGENEOUS CATALYTIC OXIDATION OF PROPENE TO ACETONE AND BUTENE-1 TO BUTANONE IN THE PRESENCE OF PALLADIUM AND MOLYBDOVANADOPHOSPHORIC HETEROPOLY ACID
E.G. Zhizhina, M.V. Simonova, V.F. Odyakov, K.I. Matveev
Appl. Catal., A, 319(1) (2007) pp. 91-97.
Oxidation of propene to acetone and butene-1 to butanone in aqueous solutions was studied in the presence of homogeneous catalysts Pd + HPA-x (HPA-x = H3+xPVxMo12−xO40 having Keggin composition, x = 1–4). The reaction order with respect to alkenes is 1, to palladium is 0.5 for propene and 0.66 for butene-1, respectively. The rate of alkene oxidation does not depend on concentration of HPA-x and acidity of catalyst solution. Alkenes are also successfully oxidized in the presence of new catalysts Pd + HPA-x′ containing modified high-vanadium non- Keggin HPA-x′ (x′ > 4). The HPA-x′ solutions have improved thermal stability and are very promising for oxidation of the lower alkenes. Kinetic peculiarities of oxidation of both alkenes in the presence of solutions of HPA-x′ and HPA-x are similar.
HYDROGEN PEROXIDE AND OXYGENHYDROGEN OXIDATION OF AROMATIC COMPOUNDS IN CATALYTIC SYSTEMS CONTAINING HETEROPOLY COMPOUNDS
N.I. Kuznetsova, N.V. Kirillova, M.Yu. Smirnova*, L.I. Kuznetsova, V.A. Likholobov* (*Institute of Hydrocarbon Processing, Novosibirsk, Russia)
J. Hazard. Mater., 146(3) (2007) pp. 569-576.
Hydrogen peroxide and Pt activated mixture of gaseous O2 and H2 have been applied to oxidation of aromatic compounds in the presence of red-ox active heteropoly compounds in the form of acid H4PMo11VO40 and tetrabuthylammonium (TBA) salts TBA4PMo11VO40 and TBA4HPW11Fe(OH)O39. Benzene, toluene and phenol were subjected to hydroxylation of the ring, that was accompanied by secondary oxidation in reaction with hydrogen peroxide. Oxygenation of toluene was equally directed to the ring and to methyl group. The total reactivity of substrates was increased in order of benzene < toluene < phenol in oxidation by both O2/H2 and H2O2, that indicated identical nature of active intermediates for both oxidants. It was suggested HPC bonded radical species to be responsible for oxidation of hydrocarbons.
AEROBIC OXIDATIONS OF α-PINENE OVER COBALT-SUBSTITUTED POLYOXOMETALATE SUPPORTED ON AMINO-MODIFIED MESOPOROUS SILICATES
N.V. Maksimchuk, M.S. Melgunov, Yu.A. Chesalov, J. Mrowiec-Białoń*, A.B. Jarzębski*, O.A. Kholdeeva (*Institute of Chemical Engineering, Gliwice, Poland)
J. Catal., 246(2) (2007) pp. 241-248.
Co-containing polyoxometalate [Bu4N]4H[PW11Co(H2O)O39] (Co-POM) was supported on various NH2-modified mesoporous silicate matrixes (SBA-15, MCF, and SiO2-xerogel). The catalysts were characterized by elemental analysis, N2 adsorption, DRS–UV, and FTIR spectroscopy. α-Pinene autoxidation and its cooxidation with isobutyraldehyde (IBA) over the supported Co-POM catalysts have been studied and compared with the corresponding processes in the presence of the homogeneous Co-POM. The autoxidation process affords allylic oxidation products, the selectivity to verbenol/verbenone decreases with alkene conversion and attains 70% at 20% conversion and 40% at 46% conversion. The catalysts can be used repeatedly without loss of the activity and selectivity during several catalytic cycles. Co-oxidation of α-pinene and IBA produces selectively α-pinene epoxide with up to 94% selectivity at 96% alkene conversion. The catalysts can be regenerated by evacuation.
DITITANIUM-CONTAINING 19-TUNGSTODIARSENATE(III) [Ti2(OH)2As2W19O67(H2O)]8-: SYNTHESIS, STRUCTURE, ELECTROCHEMISTRY, AND OXIDATION CATALYSIS
F. Hussain*,***, B.S. Bassil*, U. Kortz*, O.A. Kholdeeva, M.N. Timofeeva, P. de Oliveira**, B. Keita**, L. Nadjo** (*International University Bremen, Bremen, Germany; **d'Electrochimie et Photoélectrochimie Université Paris-Sud, Orsay Cedex, France; ***University of Melbourne, Parkville, Victoria, Australia)
Chem. Eur. J., 13(17) (2007) pp. 4733-4742.
The dititanium-containing 19-tungstodiarsenate(III) [Ti2(OH)2As2W19O67(H2O)]8- (1) has been synthesized and characterized by IR, TGA, elemental analysis, electrochemistry, and catalytic studies. Single-crystal X-ray analysis was carried out on Cs8[Ti2(OH)2As2W19O67(H2O)] 2 CsCl 12 H2O (Cs-1), which crystallizes in the monoclinic system, space group P21/m, with a=12.7764(19), b=19.425(3), c=18.149(3) Å, β=110.234(3)°, and Z=2. Polyanion 1 comprises two (B-α-AsIIIW9O33) Keggin moieties linked through an octahedral {WO5(H2O)} fragment and two unprecedented square-pyramidal {TiO4(OH)} groups, leading to a sandwich-type structure with nominal C2v symmetry. Synthesis of 1 was accomplished by reaction of TiOSO4 and K14[As2W19O67(H2O)] in a 2:1 molar ratio in aqueous, acidic medium (pH 2). Polyanion 1 could also be isolated as a tetra-n-butyl ammonium (TBA) salt, {(n-C4H9)4N}5H3[Ti2(OH)2As2W19O67(H2O)] (TBA-1). TBA-1 was studied by cyclic voltammetry in acetonitrile (MeCN) solutions containing 0.1 M LiClO4 and compared with the results obtained with Cs-1 in aqueous media. In MeCN, the TiIV and WVI waves could not be separated distinctly. An important adsorption phenomenon on the glassy carbon working electrode was encountered both in cyclic voltammetry and in controlled potential electrolysis and was confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) studies on a carbon film. TBA-1, dissolved in MeCN, reacts with H2O2 to give peroxo complexes stable enough for characterization by UV-visible spectroscopy, cyclic voltammetry, and EQCM. TBA-1 shows high catalytic activity (TOF=11.3 h-1) in cyclohexene oxidation with aqueous H2O2 producing products typical of a heterolytic oxidation mechanism. The stability of TBA-1 under turnover conditions was confirmed by using IR, UV-visible spectroscopy as well as cyclic voltammetry.
STUDY OF SYNTHESIS GAS PRODUCTION OVER STRUCTURED CATALYSTS BASED ON LaNi(Pt)Ox- AND Pt(LaPt)-CeO2-ZrO2 SUPPORTED ON CORUNDUM
S.N. Pavlova, N.N. Sazonova, V.A. Sadykov, G.M. Alikina, A.I. Lukashevich, E.L. Gubanova, R.V. Bunina
Stud. Surf. Sci. Catal., 167 (2007) pp. 343-348.
Study of partial oxidation of methane (POM), steam (SR), authothermal (AR) and dry (DR) reforming of methane over catalysts containing LaNiO3 (pure or promoted by Pt) or LaPtOx/CeO2-ZrO2supported on the fragments of corundum monolith reveals that the most effective catalysts contain LaNiO3 and LaPtOx with La excess. The reduction pretreatment as well as addition of Pt to LaNiOx facilitates the formation of syngas at a lower temperature, furthermore, Pt favors a high catalyst stability preventing catalyst coking.
PERFORMANCE OF MONOLITHIC CATALYSTS WITH COMPLEX ACTIVE COMPONENT IN PARTIAL OXIDATION OF METHANE INTO SYNGAS: EXPERIMENTAL STUDIES AND MODELING
V.A. Sadykov, S.N. Pavlova, Z.Yu. Vostrikov, N.N. Sazonova, E.L. Gubanova, R.V. Bunina, G.M. Alikina, A.I. Lukashevich, L.G. Pinaeva, L.L. Gogin, S.A. Pokrovskaya, V.B. Skomorokhov, A.B. Shigarov, C. Mirodatos*, A. van Veen*, A.P. Khristolyubov**, V.Yu. Ulyanitsky*** (*Institut de Recherches sur la Catalyse, Villeurbanne, France; **Russian Federal Nuclear Center – All-Russian Scientific Research Institute of Experimental Physics, Sarov, Russia; ***Institute of Hydrodynamics, Novosibirsk, Russia)
Stud. Surf. Sci. Catal., 167 (2007) pp. 361-366.
Experimental studies and modeling demonstrated importance of the heat and mass transfer for the process of the natural gas partial oxidation into syngas at short contact times on monolithic catalysts with a complex active component Pt/LaNiO3/Ce-Zr-La-O. A simplified approach for modeling based upon using rate constants for the reactions of methane transformation into syngas estimated for separate structural elements of monolithic catalysts in nearly isothermal conditions was successfully verified. This approach opens the way for optimization of performance of syngas generators equipped with catalysts containing active components of any complexity.
DESIGN OF STRUCTURED CATALYSTS BASED ON METALLIC MONOLITHS FOR SYNGAS PRODUCTION VIA PARTIAL OXIDATION OF NATURAL GAS
V.A. Sadykov, S.N. Pavlova, O.I. Snegurenko, Z.Yu. Vostrikov, S.F. Tikhov, V.A. Kuzmin, V.N. Parmon, V.Yu. Ulyanitsky*, O.F. Brizitsky**, A.P. Khristolubov**, V.Yu. Terentiev** (*Institute of Hydrodynamics, Novosibirsk, Russia; **Russian Federal Nuclear Center – All-Russian Scientific Research Institute of Experimental Physics, Sarov, Russia)
Stud. Surf. Sci. Catal., 172 (2007) pp. 241-244.
Structured catalysts based on metallic supports of different types with a high thermal conductivity were designed. The metal monolithic supports were made from a heat-resistant foil or gauze coated with a protective layer of Al2O3 or ZrO2 using blast dusting. To prepare catalysts, Ce-Zr-La-O and LaNiOx promoted with Pt were successively supported on monoliths. A high and stable performance of these catalysts in the partial oxidation of methane (POM) at short contact times in the autothermal mode was demonstrated. In the reactor with a heat exchanger these catalysts operate without any heat preheat at very high gas velocities in the autothermal mode.
Pt-SUPPORTED NANOCRYSTALLINE CERIAZIRCONIA DOPED WITH La, Pr OR Gd: FACTORS CONTROLLING SYNGAS GENERATION IN PARTIAL OXIDATION/AUTOTHERMAL REFORMING OF METHANE OR OXYGENATES
V.A. Sadykov, N.V. Mezentseva, G.M. Alikina, A.I. Lukashevich, Yu.V. Borchert*, T.G. Kuznetsova, V.P. Ivanov, S.N. Trukhan, E.A. Paukshtis, V.S. Muzykantov, V.L. Kuznetsov, V.A. Rogov, J. Ros**, E. Kemnitz***, K. Sheurell*** (*University of Bremen, Bremen, Germany; **University of Limerick, Limerick, Ireland; ***Humboldt University, Berlin, Germany)Solid State Phenomena, 128 (2007) pp. 239-248.
Nanocrystalline CeO2-ZrO2 (Ce:Zr 1:1) samples doped with La, Pr or Gd cations (containing up to 30 at.%) were prepared via the Pechini route. Pt (1.4 wt.%) was supported via impregnation with H2PtCl6 solution followed by drying and calcination. The samples’ surface features were studied by SIMS and FTIRS of adsorbed CO. The oxygen mobility was characterized by the dynamic oxygen isotope exchange and H2 TPR. Catalytic activity was studied in the flow installation using diluted feeds (0.7% CH4 +0.5% O2 or 1% C3H6O + 0.5% O2 +0.5% H2O in He). In the selective oxidation of methane (POM), the catalytic activity correlates with Pt dispersion controlled by the oxidized sample’s ability to stabilize Pt2+ cations as precursors of small reactive Pt clusters formed under reaction conditions. This is favoured by a larger doping cation (La) and a developed network of nanodomain boundaries. At comparable Pt dispersion, the highest performance was demonstrated by a La-doped system, which correlates with the highest surface/near-surface oxygen mobility controlled by the strength of Ce-O bonds in the surface layer. In the autothermal reforming of acetone, the activity trends differ from those in POM because of the more prominent role of the oxygen mobility required to prevent surface coking.
NANOCRYSTALLINE DOPED CERIA-ZIRCONIA FLUORITE-LIKE SOLID SOLUTIONS PROMOTED BY Pt: STRUCTURE, SURFACE PROPERTIES AND CATALYTIC PERFORMANCE IN SYNGAS GENERATION
V.A. Sadykov, N.V. Mezentseva, G.M. Alikina, A.I. Lukashevich, V.S. Muzykantov, T.G. Kuznetsova, L.Ch. Batuev, M.A. Fedotov, E.M. Moroz, D.A. Zyuzin, V.P. Kolko, V.V. Kriventsov, V.P. Ivanov, A.I. Boronin, E.M. Pazhetnov, V.I. Zaikovskii, A.V. Ishchenko, V.A. Rogov, J. Ross*, E. Kemnitz** (*University of Limerick, Limerick, Ireland; **Humboldt University, Berlin, Germany)
Mater. Res. Soc. Symp. Proc., 988 (2007) QQ06-04.
Nanocrystalline ceria-zirconia samples doped with rare-earth (Gd, Pr, Sm, La) cations were prepared via modified Pechini route. Effect of their real structure and surface composition characterized by a combination of sophisticated physical methods (XRD, TEM+EDX, EXAFS, WAXS, UV-Vis, XPS, SIMS) on the mobility and reactivity of the lattice oxygen estimated by oxygen isotope exchange, H2, CH4 and CO TPR was analyzed. For the reaction of acetone autothermal reforming into syngas, catalytic activity correlates rather well with the oxygen mobility controlled by the type and content of a dopant.
DESIGN OF ANODES FOR IT SOFC: EFFECT OF COMPLEX OXIDE PROMOTERS AND Pd ON ACTIVITY AND STABILITY IN METHANE STEAM REFORMING OF Ni/YSZ (ScSZ) CERMETS
V.A. Sadykov, N.V. Mezentseva, R.V. Bunina, G.M. Alikina, A.I. Lukashevich, V.A. Rogov, E.M. Moroz, V.I. Zaikovskii, A.V. Ishchenko, O.F. Bobrenok*, A. Smirnova**, J. Irvine***, O.D. Vasylyev**** (*Institute of Thermophysics, Novosibirsk, Russia; **University of Connecticut, Connecticut, USA; ***University of St. Andrews, St. Andrews, UK; ****Institute of Problems of Material Science, Kiev, Ukraine)
Mater. Res. Soc. Symp. Proc., 972 (2007) AA03-06.
Effect of fluorite-like or perovskite-like complex oxide promoters and Pd on the performance of Ni/8YSZ and Ni/ScSZ anode materials in CH4 steam reforming (SR) or selective oxidation (SO) by O2 into syngas was studied. The spatial uniformity of dopants distribution in composites was controlled by TEM combined with EDX analysis, while the lattice oxygen mobility and reactivity were estimated by CH4 and H2 temperature-programmed reduction (TPR). The oxide promoters suppress the coke deposition even at stoichiometric H2O/CH4 ratio, while doping by Pd ensures a good performance at moderate (~550°C) temperatures required for the Intermediate– Temperature Solid Oxide Fuel Cells (IT SOFC) operation.
DOPED NANOCRYSTALLINE Pt-PROMOTED CERIA-ZIRCONIA AS ANODE CATALYSTS FOR IT SOFC: SYNTHESIS AND PROPERTIES
V.A. Sadykov, N.V. Mezentseva, G.M. Alikina, A.I. Lukashevich, V.S. Muzykantov, R.V. Bunina, A.I. Boronin, E.M. Pazhetnov, E.A. Paukshtis, V.V. Kriventsov, A. Smirnova*, O.D. Vasylyev**, J. Irvine***, O.F. Bobrenok****, V.I. Voronin*****, I.F. Berger***** (*University of Connecticut, Connecticut, USA; **Institute of Problems of Material Science, Kiev, Ukraine; ***University of St. Andrews, St. Andrews, UK; ****Institute of Thermophysics, Novosibirsk, Russia; *****Ural State University, Ekaterinburg, Russia)
Mater. Res. Soc. Symp. Proc., 1023 (2007) JJ02-07.1-6.
Ceria-zirconia samples doped with Gd, Pr, Sm, or La cations were prepared via Pechini route and promoted by Pt. Effect of their real structure and surface properties (characterized by neutronography, EXAFS, XPS, FTIRS of adsorbed CO) on the mobility and reactivity of the lattice oxygen (by oxygen isotope exchange and CH4 TPR) was analyzed. For the reaction of CH4 steam reforming (SR), catalytic performance is determined both by Pt dispersion and lattice oxygen mobility. Ni-YSZ anodes promoted by these catalysts possess a stable and efficient performance in CH4 SR in the 600-800°C range in stoichiometric feeds without coking.
EFFECT OF COMPLEX OXIDE PROMOTERS AND Pd ON ACTIVITY AND STABILITY OF Ni/YSZ (ScSZ) CERMETS AS ANODE MATERIALS FOR IT SOFC
V.A. Sadykov, N.V. Mezentseva, R.V. Bunina, G.M. Alikina, A.I. Lukashevich, T.S. Kharlamova, V.A. Rogov, V.I. Zaikovskii, A.V. Ishchenko, T.A. Krieger, O.F. Bobrenok*, A. Smirnova**, J. Irvine***, O.D. Vasylyev**** (*Institute of Thermophysics, Novosibirsk, Russia; **University of Connecticut, Connecticut, USA; ***University of St. Andrews, St. Andrews, UK; ****Institute of Problems of Materials Science, Kiev, Ukraine)
Catal. Today, 131(1-4) (2008) pp. 226-237.
Effect of fluorite-like or perovskite-like complex oxide promoters, Pd and Cu on the performance of Ni/8YSZ and Ni/ScCeSZ anode materials in CH4 steam reforming (SR) or selective oxidation (SO) by O2 into syngas was studied. The spatial distribution of dopants in composites before and after contact with the reaction feed, features of components mutual interaction and forms of deposited coke were controlled by TEM combined with EDX analysis. The lattice oxygen mobility and reactivity were estimated by CH4 and H2 temperature-programmed reduction (TPR), and the amount of deposited carbon after operation in the feed with stoichiometric H2O/CH4 ratio was estimated by the temperature-programmed oxidation. Promoters decrease the amount of deposited coke, while doping by Pd or Cu ensures also a good and stable performance at moderate (~550°C) temperatures required for the intermediatetemperature solid oxide fuel cells (IT SOFC) operation.
DOPED NANOCOMPOSITES CeO2–LnMeO3 (Ln = Ce, La, Nd, Pr, Sm; Me = Mn, Fe, Co) FOR MIDDLE-TEMPERATURE CATHODES OF FUEL CELLS: MECHANOCHEMICAL SYNTHESIS
L.A. Isupova, E.A. Obyskalova*, V.A. Rogov, S.V. Tsybulya, G.M. Alikina, A.I. Lukashevich, V.A. Sadykov, N.F. Uvarov**, E.B. Burgina, L.S. Dovlitova, A.V. Ishchenko, V.I. Zaikovskii (*Novosibirsk State University, Novosibirsk, Russia; **Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Chem. Sustain. Devel., 15(2-1) (2007) pp. 65-71.
Nanostructured materials based on the oxide phases with perovskite and fluorite structures are prepared by mechanochemical synthesis from misch metal carbonate and transition metal oxide with stoichiometric composition of cations in initial mixture La : Me = 1 : 1. The reduction rate of the nanocomposites with hydrogen or methane is higher than the reduction rate of the individual phases. These nanostructured materials possess a high mobility of lattice oxygen. High thermal stability and high total electrical conductivity exceeding that of electrolyte (doped fluorites). Synthesized materials may be applied as cathodes in solid oxide fuel cells and membrane material in oxidation processes.
CERIA-ZIRCONIA NANOPARTICLES DOPED WITH La OR Gd: EFFECT OF THE DOPING CATION ON THE REAL STRUCTURE
V.A. Sadykov, V.V. Kriventsov, E.M. Moroz, Yu.V. Borchert*, D.A. Zyuzin, V.P. Kolko, T.G. Kuznetsova, V.P. Ivanov, A.I. Boronin, N.V. Mezentseva, E.B. Burgina, J. Ross** (*University of Bremen, Bremen, Germany; **University of Limerick, Limerick, Ireland)
Solid State Phenomena, 128 (2007) pp. 81-88.
The real structure of nanocrystalline CeO2-ZrO2 (Ce:Zr=1:1) systems prepared via the polymerized polyester precursor (Pechini) route and doped with La3+ or Gd3+ cations, up to 30 at.%, was studied by X-ray powder diffraction, EXAFS and Raman spectroscopy and the surface features characterized by XPS and SIMS. Undoped CeO2-ZrO2 system revealed nanoscale heterogeneity, perhaps due to the co-existence of Zr- or Ce-enriched domains. With large La3+ dopant the system remains bi-phasic within the studied ranges of composition, incorporation of the smaller Gd3+ cation stabilizes the single-phase solid solution. For both systems, the increase of dopant content was accompanied by a decline of domain size and an increase of the average lattice parameter of fluorite-like phases. Depletion of the surface layer by smaller Zr4+ cations was observed, while the surface content of a doping cation is either, close to that in the bulk (La) or below it (Gd). Such a spatial distribution of components results in some ordering of cations within the lattice. It is reflected in different modes of rearrangement of oxygen coordination polyhedra with the Gd or La content (distances and coordination numbers by EXAFS), and specificity of XRD patterns not conforming to a simple model with statistical distribution of oxygen vacancies.
SYNTHESIS AND PROPERTIES OF NANOCOMPOSITES WITH MIXED IONIC–ELECTRONIC CONDUCTIVITY ON THE BASIS OF OXIDE PHASES WITH PEROVSKITE AND FLUORITE STRUCTURES
V.A. Sadykov, Yu.V. Borchert*, G.M. Alikina, A.I. Lukashevich, N.V. Mezentseva, V.S. Muzykantov, E.M. Moroz, V.A. Rogov, V.I. Zaikovskii, D.A. Zyuzin, N.F. Uvarov**, A.V. Ishchenko, V.V. Zyryanov**, A. Smirnova*** (*University of Bremen, Bremen, Germany; **Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; ***University of Connecticut, Connecticut, USA)
Glass Phys. Chem., 33(4) (2007) pp. 320-334.
Nanocomposites consisting of phases with fluorite (doped CeO2) and perovskite (LaMnO3, GdMnO3) structures are synthesized using the method of ester polymeric precursors (the Pechini method) and two sources of rare-earth elements (Ln), such as pure cerium and gadolinium salts or a commercial mixture of rare-earth carbonates containing La, Ce, Pr, Nd, and Sm cations. The genesis of the nanocomposite structure as a function of the sintering temperature is investigated using X-ray diffraction and electron microscopy. It is revealed that the genesis of the nanocomposite structure is governed, in many respects, by the fact that the decomposition of the ester polymeric precursor leads to the formation of a metastable phase, namely, a fluorite-like solid solution based on ceria with an excess concentration of the cations Ln3+(Ln3+= La3+, Pr3+, Nd3+, Sm3+) as compared to the equilibrium concentration. As a result, the perovskite phase (identified by X-ray diffraction analysis) is formed only after the subsequent annealing at temperatures higher than 800°C, when Ln3+ cations escape from particles of the solid solution. It is demonstrated that, at annealing temperatures of up to 1100°C, particles of both phases have nanometer sizes and are characterized by a uniform spatial distribution necessary for percolation. The nanocomposites possess a high total electrical conductivity and a high mobility of lattice oxygen. The reduction rate of the nanocomposites with hydrogen or methane is higher than the reduction rate of the individual phases. The characteristics of the nanocomposites prepared from the commercial mixture of rare-earth carbonates are better than those of the samples synthesized from the pure salts.
SCANDIA–STABILIZED ZIRCONIA: EFFECT OF DOPANTS ON SURFACE/GRAIN BOUNDARY SEGREGATION AND TRANSPORT PROPERTIES
A. Smirnova*, V.A. Sadykov, V.S. Muzykantov, N.V. Mezentseva, V.P. Ivanov, V.I. Zaikovskii, A.V. Ishchenko, N. Sammes*, O.D. Vasylyev**, J. Kilner***, J. Irvine****, V.G. Vereschak*****, I. Kosacki******, N.F. Uvarov*******, V.V. Zyryanov******* (*University of Connecticut, Connecticut, USA; **Institute of Problems of Material Science, Kiev, Ukraine; ***Imperial College of London, UK; ****University of St. Andrews, St. Andrews, UK; *****Ukrainian State Chemical-Technological University, Dnipropetrovsk, Ukraine; ******Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA; *******Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Mater. Res. Soc. Symp. Proc., 972 (2007) AA10-05.
The nanocrystalline samples of 10wt%Scandia stabilized Zirconia (10ScSZ) and 1wt%Ceria doped ScSZ (1Ce10ScSZ) prepared via co-precipitation route were characterized and compared to commercially available samples regarding their transport properties and electrical conductivity. The results of oxygen isotope experiments show that for Zr-based electrolytes, the rate of heteroexchange is lower than that for Sm-doped ceria. The results of Secondary Ions Mass Spectrometry (SIMS) indicate that all admixed components are present both in the surface layer and the bulk of the studied samples with pronounced segregation on the grain boundary. The highest total conductivity is observed for DKKK sample. In the range of 600-400°C the highest conductivity observed for synthesized nanocrystalline 1Ce10ScSZ sample is explained by the effect of segregated Scandia doped Ceria surface layers.
LOW-TEMPERATURE SYNTHESIS METHODS OF DOPED APATITE-TYPE LANTHANUM SILICATES
T.S. Kharlamova, S.N. Pavlova, V.A. Sadykov, O.B. Lapina, D.F. Khabibulin, T.A. Krieger, V.I. Zaikovskii, A.V. Ishchenko, M.V. Chaikina*, Ch. Argirusis** (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia;**Clausthal University of Technology, Clausthal-Zellerfeld, Germany)
J. Chem. Eng. Japan, 40(13) (2007) pp. 1187-1191. 158
Al- and Sr-doped apatite-type lanthanum silicates (ATLS) have been prepared using mechanochemical activation (MA) and Pechini (Pe) methods. MA of a stoichiometric mixture in the high-power planetary ball mill provides the formation of a high purity crystalline ATLS at room temperature after 20–35 min activation. The phase composition and local structure of doped ATLS are determined by milling time and the dopant content. 5 min MA of carbonate precursors obtained via Pe method results in the formation of a single-phase ATLS at 900°C.
MECHANOCHEMICAL SYNTHESIS OF SOLID SOLUTIONS BASED ON ZrO2 AND THEIR ELECTRICAL CONDUCTIVITY
V.V. Zyryanov*, N.F. Uvarov*, V.A. Sadykov (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Glass Phys. Chem., 33(4) (2007) pp. 393-401.
Zirconia- and scandia-based complex solid solutions predominantly with a monoclinic structure are prepared by mechanochemical synthesis. The dense ceramic materials, which, for the most part, have a cubic structure with grain sizes of 250-400 nm and possess good mechanical properties, are produced by sintering submicron fractions of the powders under relatively mild conditions at temperatures of 1633- 1653 K. It is revealed that the powders are characterized by nanostructuring due to the complex composition and the chemical inhomogeneity. This nanostructuring is partially retained upon rapid sintering of the ceramic powders. The nanostructured ceramic materials possess a high low-temperature conductivity, which decreases after annealing. Unlike conventional ceramic materials, the nanostructured ceramic materials have identical activation energies for bulk and grain-boundary electrical conduction. The high-temperature electrical conductivity of the nanostructured ceramic materials is rather low because of the small grain sizes and impurities of the monoclinic phase.
DESIGN OF MULTILAYER CERAMIC MIEC MEMBRANES
V.V. Zyryanov*, V.A. Sadykov, G.M. Alikina (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Sep. Sci. Technol., 42(13) (2007) pp. 2849-2861.
The development of multilayer mixed conducting oxide membranes on porous dead-end tubular mineralbased glass-ceramic supports is presented. Nanopowders of compatible complex perovskites and fluorites as membrane materials were obtained by mechanochemical synthesis. The deposition of oxide ceramic porous and dense layers was carried out by casting of slurries in organic medium, prepared from narrow fractions of agglomerated powders. A linear dependence between the sintering temperature Ts and calculated effective melting point T*m for complex perovskites and fluorites was revealed that allowed to propose a simple rule for the synthesis of complex oxides with required Ts. Dead-end tubular supports were produced by casting from selected kaolins with organic/inorganic additives. The misfit in sintering temperatures of porous substrate and MIEC ceramic layers was eliminated by modification of substrate and heavily doping of mixed oxides. The elimination of shrinkage misfit between the porous substrate and ceramic layers was achieved by optimization of operation conditions and compositions of both substrate and ceramics. Almost gas-tight cost efficient catalytic membrane reactors CMRs with large operation surface 30 cm2 and good prospects for up-scaling were produced and tested.
PREPARATION OF 2-METHYL-1,4- NAPHTHOQUINONE (VITAMIN K3) BY CATALYTIC OXIDATION OF 2-METHYL-1- NAPHTHOL IN THE PRESENCE OF IRON PHTHALOCYANINE SUPPORTED CATALYST
O.V. Zalomaeva, O.A. Kholdeeva, A.B. Sorokin* (*Institut de Recherches sur la Catalyse, CNRS, Villeurbanne, France)
Comptes Rendus Chim., 10(7) (2007) pp. 598-603.
Iron tetrasulfophthalocyanine (FePcS) supported catalyst was prepared by covalent grafting onto amino-modified silica by a novel practical one-pot method using activation of sulfonate groups of FePcS by triphenylphosphine triflate. FePcS/SiO2 in combination with tBuOOH behaved as an efficient catalyst for the oxidation of 2-methyl-1-naphthol to 2-methyl-1,4-naphthoquinone, vitamin K3. To optimize the catalytic system, the influence of different reaction parameters on the efficiency of this oxidation has been studied. Vitamin K3 was obtained with 59% selectivity at 96% conversion of 2-methyl- 1-naphthol using only 0.5 mol% of catalyst. 18O labelling experiments indicate a non-radical mechanism for this oxidation.
NEW ROUTES TO VITAMIN K3
O.A. Kholdeeva, O.V. Zalomaeva, A.B. Sorokin*, I.D. Ivanchikova, C.D. Pina**, M. Rossi** (*Institut de Recherches sur la Catalyse, Villeurbanne, France; **cDipartimento di Chimica Inorganica, Metallorganica e Analitica, Universitа degli Studi di Milano, Italy)
Catal. Today, 121(1-2) (2007) pp. 58-64.
New clean and efficient methods for the production of 2-methyl-1,4-naphthoquinone (MNQ, menadione, vitamin K3) based on the oxidation of 2-methyl-1-naphthol (MNL) with cheap and environmentally benign oxidants, aqueous hydrogen peroxide, tert-butyl hydroperoxide and molecular oxygen, using three types of true heterogeneous catalysts, such as hydrothermally stable mesoporous titanium-silicate Ti-MMM-2, silica supported iron phthalocyanine and supported gold nanoparticles, are reported. Advantages and drawbacks of the catalytic systems are discussed. Surprisingly, non catalytic oxidation of MNL with molecular oxygen shows superior selectivity and volume yield of MNQ compared to the known catalytic methods.
HIGHLY EFFICIENT PRODUCTION OF 2,3,5-TRIMETHYL-1,4-BENZOQUINONE USING AQUEOUS H2O2 AND GRAFTED Ti(IV)/SiO2 CATALYST
O.A. Kholdeeva, I.D. Ivanchikova, M. Guidotti*, N. Ravasio* (*CNR-ISTM, Centro CIMAINA and Dip. Chimica IMA, Milano, Italy)
Green Chem., 9 (2007) pp. 731-733.
The oxidation of 2,3,6-trimethylphenol (TMP) with aqueous H2O2 over titanium(IV) grafted on commercial mesoporous silica produces 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E precursor) with nearly quantitative yield. The grafted catalysts are prepared by a simple, affordable and cheap synthesis methodology, combine excellent activity, very high selectivity to the desired product TMBQ and good recyclability in the TMP oxidation by aqueous H2O2. All these allow considering them as perspective heterogeneous catalysts for the clean and sustainable synthesis of TMBQ.
EPR STUDY ON THE MECHANISM OF H2O2-BASED OXIDATION OF ALKYLPHENOLS OVER TITANIUM SINGLE-SITE CATALYSTS
O.V. Zalomaeva, N.N. Trukhan*, I.D. Ivanchikova, A.A. Panchenko*, E. Roduner*, E.P. Talsi, A.B. Sorokin**, V.A. Rogov, O.A. Kholdeeva (*Stuttgart University, Stuttgart, Germany; **Institut de Recherches sur la Catalyse et l’Environnement de Lyon, Villeurbanne Cedex, France)
J. Mol. Catal. A: Chem., 277(1-2) (2007) pp. 185-192.
The selective oxidation of 2,3,6-trimethylphenol (TMP) and 2-methyl-1-naphthol (MNL) with H2O2 catalyzed by titanium single-site catalysts, TiO2–SiO2 aerogel and mesostructured hydrothermally stable titanium-silicate, Ti-MMM-2, have been studied by means of EPR spectroscopic technique with spin traps. The formation of phenoxyl (naphthoxyl) and hydroxyl radical intermediates during the oxidation process have been detected using 3,5-dibromo-4- nitrosobenzene-sulfonic acid (DBNBS) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin traps, respectively. The character of the EPR spectra of the DBNBS adducts strongly depends on the nature of the organic substrate and the reaction temperature. A compilation of the EPR and by-product studies strongly supports a homolytic oxidation mechanism. Study by DR-UV–vis spectroscopy has confirmed the previously suggested chemical adsorption of phenol on the titanium center.
ACCESS TO FUNCTIONALIZED QUINONES VIA THE AROMATIC OXIDATION OF PHENOLS BEARING AN ALCOHOL OR OLEFINIC FUNCTION CATALYZED BY SUPPORTED IRON PHTHALOCYANINE
O.V. Zalomaeva, A.B. Sorokin* (*Institut de Recherches sur la Catalyse, CNRS, Villeurbanne, France)
New J. Chem., 30(12) (2006) pp. 1768-1773.
The controlled oxidation at only one position of compounds with several oxidizable sites, while keeping the other sites intact, has been demonstrated for phenols bearing alcohol or olefinic functional groups. Iron tetrasulfophthalocyanine supported on silica was found to be an efficient catalyst for the preparation of functionalized quinones under mild conditions, with tert-butylhydroperoxide as the oxidant. A novel rapid and mild one-pot procedure for the covalent grafting of iron tetrasulfophthalocyanine onto silica has been developed. The supported catalyst was characterized by chemical analysis, a specific surface study, UV-vis spectroscopy and XPS. A non-radical mechanism for this unusual selective oxidation has been revealed by 18O labelling experiments.
ENANTIOSELECTIVE CHROMATOGRAPHIC RESOLUTION AND ONE-POT SYNTHESIS OF ENANTIOMERICALLY PURE SULFOXIDES OVER A HOMOCHIRAL Zn-ORGANIC FRAMEWORK
A.L. Nuzhdin, D.N. Dybtsev*, K.P. Bryliakov, E.P. Talsi, V.P. Fedin* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Am. Chem. Soc., 129(43) (2007) pp. 12958-12959.
(R)- and (S)- enantiomers of alkyl aryl sulfoxides can be obtained by chromatographic resolution of the racemic mixtures of the sulfoxides on a microporous homochiral Zn-organic polymer or by simultaneous catalytic oxidation of the corresponding sulfides with H2O2 and enantioselective chromatographic resolution of the resulting sulfoxides in a one-pot process.
PREPARATIVE PROCEDURE FOR THE SYNTHESIS OF 4-ALLYLOXYPYRIDINE-2,6- DICARBOXYLIC ACID
S.A. Prikhod’ko*,**, I.I. Oleinik*, I.V. Oleinik*, S.S. Ivanchev, G.A. Tolstikov* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia; **Novosibirsk State University, Novosibirsk, Russia)
Russ. J. Org. Chem., 43(1) (2007) pp. 156-158.
4-Allyloxypyridine-2,6-dicarboxylic acid (I) is used as starting compound in the synthesis of 4-allyloxy-2,6-diacetylpyridine; N-arylimines derived from the latter at both carbonyl groups attract considerable interest as ligands for immobilized iron(II) complexes as highly efficient catalysts in the polymerization of ethylene. Kim et al. described a procedure for the synthesis of dicarboxylic acid I starting from 4-hydroxypyridine-2,6-dicarboxylic acid monohydrate (III) in three steps. The authors have found that acid I can be synthesized in two steps and that its yield can be raised to 89% by carrying out alkylation of anhydrous dicarboxylic acid III with allyl bromide in the presence of anhydrous potassium carbonate in a mixture of acetone with DMF. The subsequent alkaline hydrolysis of diallyl 4-allyloxypyridine- 2,6-dicarboxylate (IV) gives the target product.
DESIGN OF SCHIFF BASE-LIKE POSTMETALLOCENE CATALYTIC SYSTEMS FOR POLYMERIZATION OF OLEFINS. IV. SYNTHESIS OF 2-(ARYLIMINOMETHYL)-PYRROLE AND 7-(ARYLIMINOMETHYL)INDOLE DERIVATIVES CONTAINING CYCLOALKYL SUBSTITUENTS
A.I. Kochnev*, I.I. Oleinik*, I.V. Oleinik*, S.S. Ivanchev, G.A. Tolstikov* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. J. Org. Chem., 43(4) (2007) pp. 571-576.
Reactions of 4,6-substituted 2-cycloalkylanilines with 1H-pyrrole-2-carbaldehyde and 1H-indole-7- carbaldehyde in methanol in the presence of formic acid gave the corresponding Schiff bases which can be used as ligands for titanium and zirconium complexes.
DESIGN OF SCHIFF BASE-LIKE POSTMETALLOCENE CATALYTIC SYSTEMS FOR POLYMERIZATION OF OLEFINS. V. SYNTHESIS OF SALICYLALDEHYDE IMINE LIGANDS CONTAINING CYCLOALKYL SUBSTITUENTS
I.I. Oleinik*, I.V. Oleinik*, G.S. Zhilovskii*, S.S. Ivanchev, G.A. Tolstikov* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. J. Org. Chem., 43(11) (2007) pp. 1671-1676.
Reactions of substituted cycloalkylanilines with salicylaldehyde, 3-tert-butylsalicylaldehyde, and 3,5-di-tert-butylsalicylaldehyde in methanol in the presence of formic acid gave a series of the corresponding Schiff bases as ligands for titanium(IV) complexes.
SYNTHESIS OF SALICYLALDEHYDES BEARING BULKY SUBSTITUENTS IN THE POSITIONS 3 AND 5
A.I. Kochnev*, I.I. Oleinik*, I.V. Oleinik*, S.S. Ivanchev, G.A. Tolstikov* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. Chem. Bull., 56(6) (2007) pp. 1125-1129.
Reaction of 2,4-disubstituted phenols with paraformaldehyde in the presence of SnCl4 and 2,6-lutidine afforded a number of new salicylaldehydes, containing bulky substituents (tert-butyl, 1-phenylethyl, 1-(4-tert-butylphenyl)ethyl, α-cumyl, and trityl) in the positions 3 and 5.
SYNTHESIS OF DIIMINE LIGANDS WITH CYCLOALKYL SUBSTITUENTS BASED ON 4,6-DIBENZOFURAN-AND 4,6-DIBENZOTHIOPHENEDICARBOXALDEHYDES
I.I. Oleinik*, I.V. Oleinik*, S.S. Ivanchev, G.A. Tolstikov* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. Chem. Bull., 56(6) (2007) pp. 1174-1177.
A formic acid-catalyzed reaction of substituted cycloalkylanilines with 4,6-dibenzofuran- and 4,6-dibenzothiophenedicarboxaldehydes in methanoldichloromethane mixture afforded a number of the corresponding diimines, which can be of interest as components of catalytic systems for polymerization of olefins.
HYDROGENOLYSIS OF DIMETHYL DISULFIDE IN THE PRESENCE OF BIMETALLIC SULFIDE CATALYSTS
A.V. Mashkina, L.N. Khairulina
Kinet. Catal., 48(1) (2007) pp. 125-131.
The hydrogenolysis of dimethyl disulfide in the presence of Ni,Mo and Co,Mo bimetallic sulfide catalysts was studied at atmospheric pressure and T = 160-400°C. At T ≤ 200°C, dimethyl disulfide undergoes hydrogenolysis at the S–S bond, yielding methanethiol in 95–100% yield. The selectivity of the reaction decreases with increasing residence time and temperature due to methanethiol undergoing condensation to dimethyl disulfide and hydrogenolysis at the C–S bond to yield methane and hydrogen sulfide. The specific activity of the Co,Mo/Al2O3 catalyst in hydrogenolysis at the S–S and C–S bonds is equal to or lower than the total activity of the monometallic catalysts. The Ni,Mo/Al2O3 catalyst is twice as active as the Ni/Al2O3 + Mo/Al2O3 or the cobalt–molybdenum bimetallic catalyst.
SUPERACIDIC ACTIVATION OF QUINOLINE AND ISOQUINOLINE; THEIR REACTIONS WITH CYCLOHEXANE AND BENZENE
K.Yu. Koltunov, G.K.S. Prakash*, G. Rasul*, G.A. Olah* (*University of Southern California, Los Angeles, California)
J. Org. Chem, 72(19) (2007) pp. 7394-7397.
Quinoline (1) and isoquinoline (2), upon activation by strong acids, lead to intermediate N,C-diprotonated dications, which are involved in reactions with weak nucleophiles. Thus, 1 and 2 undergo selective ionic hydrogenation with cyclohexane in CF3SO3H-SbF5, HBr-AlBr3-CH2Br2, or HCl-Al3l3-CH2Cl2 acid systems to give their 5,6,7,8-tetrahydro derivatives. They also readily condense with benzene in the presence of HBr-AlBr3 or HCl-AlCl3 to provide 5,6,7,8-tetrahydro-5,7- diphenylquinoline and 5,6,7,8-tetrahydro-6,8- diphenylisoquinoline, respectively.
SUPERACIDIC AND HUSY-ZEOLITE ACTIVATION OF 1,3-INDANDIONE: REACTIONS WITH BENZENE AND CYCLOHEXANE
K.Yu. Koltunov
Tetrahedron Lett., 48(32) (2007) pp. 5631-5634.
1,3-Indandione readily condenses with benzene and undergoes selective ionic hydrogenation with cyclohexane when activated by superacids, such as CF3SO3H, AlC33 and AlBr3 to give 3,3-diphenyl-1- indanone and 1-indanone, respectively. Combination of these reactions in ‘one-pot’ yields 3-phenyl-1-indanone. In addition, similar reactions have been carried out using the regenerable solid acid, HUSY-zeolite, providing an effective excess of acidic sites. The mechanism of these reactions, with potential involvement of superelectrophilic dicationic intermediates, is discussed.
2,2′-BIPYRIDINE AND RELATED N-CHELANTS AS VERY EFFECTIVE PROMOTERS FOR Cu CATALYSTS IN THE DECARBOXYLATION
A.S. Lisitsyn
Appl. Catal., A, 332(1) (2007) pp. 166-170.
Effect of 2,2′-bipyridine (bipy) and analogous ligands on decarboxylation of 2,4-dimethylbenzoic (DMBA) and 4-hydroxybenzoic acids with Cu catalysts has been compared with that of quinoline. The chelating ligands were shown to exceed the traditional promoter in efficiency by two to three orders of magnitude per a mol basis. In combination with bipy-like promoters, Cu catalysts ensured complete conversion of even the low reactive DMBA for 15–30 min and gave expected product in >95% yield (S/C 40–100, Ph2O as solvent, 250°C). In the decarboxylation of individual aromatic acids, the (Cu + bipy) system greatly surpassed carbon and Pd/C catalysts as well, but lost activity in solutions of natural acidic mixtures. The later was assigned to reduction of Cu ions by H-donor constituents of such mixtures.
POSSIBLE PREBIOTIC SYNTHESIS OF MONOSACCHARIDES FROM FORMALDEHYDE IN PRESENCE OF PHOSPHATES
A.N. Simonov, O.P. Pestunova, L.G. Matvienko, V.N. Snytnikov, O.A. Snytnikova*, Yu.P. Tsentalovich*, V.N. Parmon (*International Tomography Center, Novosibirsk, Russia)
Adv. Space Res., 40(11) (2007) pp. 1634-1640.
Condensation of formaldehyde and lower carbohydrates (glycolaldehyde, glyceraldehyde, and dihydroxyacetone) is effectively catalyzed by heterogeneous and homogeneous phosphates in neutral aqueous medium. The interaction of formaldehyde and dihydroxyacetone leads to the preferential formation of 3-pentulose and erythrulose with yields of 40% and 45%, respectively. In absence of formaldehyde, the condensation of glycolaldehyde and glyceraldehyde catalyzed by phosphates leads to the formation of ribose and fructose. The possibility of formation of higher monosaccharides from pure formaldehyde in the course of the combined photochemical and phosphate-catalyzed reactions in plausible prebiotic conditions was demonstrated.
ABIOGENIC SYNTHESIS OF PREBIOTIC MATTER FOR THE EARTH’S BIOSPHERE AS A STAGE OF SELF-ORGANIZATION ON AN ASTROPHYSICAL AND PALEONTOLOGICAL TIME SCALE
V.N. SnytnikovPaleontological J., 41(5) (2007) pp. 473-480.
Existing data suggest that an early circumstellar preplanetary disk was the most likely location for primary abiogenic synthesis of prebiotic organic matter from simple molecules along with the “RNA world” and the origin of life. This paper discusses the stages of self-organization that have resulted in the Earth’s modern biosphere, and the relationships between astrophysical and paleontological events in evolution.
SELECTIVE SYNTHESIS OF ERYTHRULOSE AND 3-PENTULOSE FROM FORMALDEHYDE AND DIHYDROXYACETONE CATALYZED BY PHOSPHATES IN A NEUTRAL AQUEOUS MEDIUM
A.N. Simonov, L.G. Matvienko, O.P. Pestunova, V.N. Parmon, N.A. Komandrova*, V.A. Denisenko*, V.E. Vas’kovskii* (Pacific Institute of Bioorganic Chemistry, Vladivostok, Russia)
Kinet. Catal., 48(4) (2007) pp. 550-555.
The aldol condensation of formaldehyde and the lower carbohydrate dihydroxyacetone in a neutral aqueous medium is effectively catalyzed by solid compounds (hydroxylapatite and calcium phosphate and carbonate), natural minerals (apatite and vivianite), and soluble phosphates. In excess formaldehyde, the decrease in the concentration of the lower carbohydrate is described by a first-order rate law with respect to dihydroxyacetone. The major products of the reaction between formaldehyde and dihydroxyacetone in the presence of the above catalysts are erythrulose (45–50% selectivity) and 3-pentulose (35–40% selectivity). Branched pentulose and hexulose are also identified among the reaction products.
PHOTOCATALYTIC OXIDATION OF 1,1-DIMETHYL HYDRAZINE VAPOURS ON TiO2: FTIR IN SITU STUDIES
P.A. Kolinko, D.V. Kozlov, A.V. Vorontsov, S.V. Preis* (*Lappeenranta University of
Technology, Lappeenranta, Finland)
Catal. Today, 122(1-2) (2007) pp. 178-185.Gas-phase photocatalytic oxidation (PCO) of unsymmetrical dimethyl hydrazine (UDMH) in a batch reactor using TiO2 as the photocatalyst was studied with in situ FTIR method. Carbon dioxide, water, nitric acid and nitrogen were detected as the ultimate PCO products of UDMH. Adsorbed N2O species were detected as the main surface intermediates. The formation of the extremely toxic intermediate, nitrosodimethylamine (CH3)2NNO, was not observed. The reaction mechanism based on detected products distribution, kinetics analysis and previously published data is discussed. Long-term experiments were carried out to determine the photocatalyst stability in PCO of UDMH: the catalyst exhibited stable performance; the rate of deactivation was low due to transformation of nitrogen mainly to N2. Only 10% of UDMH nitrogen was transformed to HNO3 in adsorbed form.
PHOTOCATALYTIC OXIDATION OF VX-SIMULATION SUBSTANCE
E.A. Kozlova, A.V. Vorontsov, G. Rima*, C. Lion**, S. Preis*** (*Université Paul Sabatier, Toulouse, France; **Institut de Topologie et de Dynamique des Systèmes de I'Université Paris, Paris, France; ***Lappeenranta University of Technology, Lappeenranta, Finland)
Water Sci. Techn., 55(12) (2007) pp. 133-138.
Experimental studies of photocatalytic oxidation (PCO) by air oxygen of VX-gas simulation substance cysteamine-S-phosphate sodium salt (NaHPO3S-CH2-CH2-NH2, CPSS) at different initial concentrations and pH were undertaken. PCO ultimately resulted in complete mineralization of CPSS. The PCO by-products of CPSS include acetate, oxalate and trace amounts of formate ions. The formation rates of acetate and phosphate were equal to the rate of degradation of CPSS, which indicates easy breakage of P-S, C-S and C-N bonds. Sulphate was formed slower due to stepwise oxidation of reduced sulphur. Amino group, generally transformed to ammonia, was partially oxidised to nitrite and nitrate in alkaline media. The fastest mineralisation in terms of both TOC degradation and phosphate formation was observed at pH 9.5. Under neutral media conditions, the PCO rate increased linearly with the CPSS concentration increase. The maximum efficiency by TOC degradation was observed as big as 77 mg per Wh of incident UV flux.
PHOTOCATALYTIC AIR CLEANING FROM AUTOMOTIVE CONTAMINANTS
D.V. Kozlov, Yu.V. Trofimenko, V.P. Dubovitskaya, A.V. Vorontsov
Catal. Ind., 6 (2006) pp. 19-28.
The photocatalytic method of air cleaning in internal spaces of motor vehicles from emissions is considered. A new photo-catalytic air cleaner is described. It consists of UV-lamp of 36 W in capacity and photocatalyst IK 12-31 applied on platelike packaged carriers. The photocatalyst contains photoactive TiO2 (anatase, SBET = 340 m2/g) and highdispersed platinum in amount of 0,2 wt %. The photocatalytic air cleaner was tested in the process of air cleaning from CO, NOx, SO2 as well as acetone, heptane, acetaldehyde, and toluene vapors in a closed chamber simulating the passenger compartment. It provides the air purification from indicated substances by oxidizing the organic substances and CO into CO2, and NOx and SO2 into corresponding acids adsorbed on the catalyst surface. The quantum efficiency of oxidation varies within 2÷28 % for different substances at initial contaminant concentration 70-800 mg/m3. As compared with the less efficient adsorption methods, it can reach deep cleaning from CO and light hydrocarbons. When operating with CO and hydrocarbons, the photocatalytic filter regeneration is not required and its time of operation is restricted by the operational life of the lamp (1-2 years). A conclusion is made on efficiency of photocatalytic filter application for air cleaning in passenger compartments of all types of vehicles. Implementation and efficient use of the photocatalytic filters requires integration of ventilation into the system, this can be obtained in joint developments with the manufacturers of vehicles.
OPPOSITE EFFECT OF GAS PHASE H2O2 ON PHOTOCATALYTIC OXIDATION OF ACETONE AND BENZENE VAPORS A.V. VorontsovCatal. Commun., 8 (2007) pp. 2100-2104
.The effect of additions of gas phase H2O2 was measured for gas phase photocatalytic oxidation of organic vapors. Photocatalytic oxidation of benzene vapor over TiO2 in a flow reactor resulted in a quick catalyst deactivation. Additions of gas phase H2O2 into the reactor feed provided enhanced and sustained oxidation of benzene vapor. The increase of inletH2O2 vapor concentration from 0 to about 1000 ppm led to the one order of magnitude growth of benzene vapor complete oxidation rate. The highest rate of 1.1 nmol/s was observed at C6H6 concentration 124 ppm and H2O2 concentration 1000 ppm. In the case of acetone vapor photocatalytic oxidation, the rate of complete oxidation in the flow reactor decreased with an increase of gas phase H2O2 inlet concentration. TiO2 Degussa P25 provided higher oxidation rate in the presence of H2O2 than pure anatase TiO2.
INFLUENCE OF MESOPOROUS AND PLATINUM MODIFIED TITANIUM DIOXIDE PREPARATION METHODS ON PHOTOCATALYTIC ACTIVITY IN LIQUID AND GAS PHASE
E.A. Kozlova, A.V. Vorontsov
Appl. Catal. B, 77(1-2) (2007) pp. 35-45.
Mesoporous titanium dioxide photocatalysts have been synthesized by template method using widely used precursors and templates with the purpose of choosing the best method for liquid and gas phase photocatalytic oxidation. Titanyl sulphate (TS) and tetrabutyl titanate (TBT) were precursors and cetyl trimethylammonium bromide (CTAB) and dodecylamine (DDA) were templates. Hydrothermal treatment temperature was optimized for the best obtained photocatalyst. The catalysts were characterized by N2 adsorption–desorption measurements, XRD and UV–vis diffuse reflectance spectroscopy. Samples obtained from TBT contained significant amounts of brookite. Activity was measured in liquid phase for dimethyl methylphosphonate (DMMP) and in gas phase for acetone complete oxidation. The highest activity in liquid phase was observed for catalyst prepared from TS and DDA and aged at 160°C. Activity was higher than that of TiO2 Degussa P25 in the low concentration range. The highest activity in gas phase was observed for catalyst prepared from TBT and CTAB. Activity of mesoporous catalysts correlates with their surface area and pore volume for gas phase reaction, whereas in the case of liquid phase DMMP oxidation, there is no sufficient correlation. The effect of DMMP initial concentration on initial oxidation rate is well fitted by Langmuir–Hinshelwood competitive adsorption model. Mesoporous catalysts possess higher adsorption constant but lower reaction rate constant than TiO2 P25. Platinum was deposited by impregnation and soft chemical reduction (SCR) or photodeposition methods (PD). Catalysts obtained by PD were 50% more active than by SCR and 4.5-fold more active than TiO2 P25 in aqueous phase. The reasons for extraordinarily high activity of this mesoporous catalyst are discussed.
ACCELERATION OF ACETONE DESTRUCTION PROCESS UNDER SYNERGISTIC ACTION OF PHOTOCATALYTIC OXIDATION AND BARRIER DISCHARGE
A.S. Besov, A.V. Vorontsov
Plasma Chem. Plasma Process., 27(5) (2007) pp. 624-634.
Separate and joint work of photocatalytic oxidation based on TiO2 and surface barrier discharge as a source of ozone and UV radiation is investigated for acetone vapors destruction under ambient air conditions. Experiments were carried out in 404 l airtight plexiglas chamber and used five different combinations of photocatalyst, barrier discharge and ultraviolet irradiation under identical initial concentration (~ 170 ppm) of acetone. It is shown for synergistic action of photocatalytic method and barrier discharge that the initial rate of acetone decomposition per watt of input power increases in more than 1.5 times compared to the most effective case of photocatalytic oxidation alone. It has been determined that under operation of plasma of barrier discharge intermediate products such as CO, acetic acid, acetaldehyde and methane nitrate (CH3NO3) are formed. These products are not detected for photocatalytic oxidation. Some features of kinetics of acetone decomposition and formation of intermediate products are revealed.
EFFECT OF TiOSO4 HYDROTHERMAL HYDROLYSIS CONDITIONS ON TiO2 MORPHOLOGY AND GAS-PHASE OXIDATIVE ACTIVITY
D.V. Bavykin*, V.P. Dubovitskaya, A.V. Vorontsov, V.N. Parmon (*University of Southampton, Southampton, UK)
Res. Chem. Intermed., 33(3-5) (2007) pp. 449-464.
The effect of synthesis conditions on morphology and catalytic activity has been studied for hydrothermal preparation of TiO2 from acidified aqueous TiOSO4 solution. It was found that the increase in TiOSO4 and H2SO4 concentration results in the increase of photocatalytic activity of produced TiO2, as it was revealed by steady-state gas-phase oxidation of acetone and ethanol vapors in a flowcirculating reactor. TiOSO4 concentration exerts strong influence on the shape of the produced TiO2 particles. At TiOSO4 concentration less than 0.1 wt%, hydrolysis gives rise to hedgehog-like agglomerates consisting of spliced-blade H2SO4 nanocrystals. At higher concentration of TiOSO4, the resultant TiO2 consists of round agglomerates of 5-10 nm primary particles. The size of secondary particles depends mainly on the H2SO4 concentration. The increase of the time of hydrothermal treatment results in the enhancement of TiO2 photocatalytic activity that reaches a maximum. Among different acids (HCl, HClO4, HNO3, H3PO4 and CH3COOH) added during hydrolysis of TiOSO4 , sulfuric and acetic acids had the best effect on photocatalytic activity of TiO2. The results obtained can help to finely tune this TiO2 preparation method in order to obtain desirable particles size, shape and activity.
EXAFS STUDY AND PHOTOCATALYTIC PROPERTIES OF UN-DOPED AND IRON-DOPED ZrO2-TiO2 (PHOTO-) CATALYSTS
M.C. Hidalgo*, G. Colon*, J.A. Navio*, A. Macias*, V.V. Kriventsov, D.I. Kochubey, M.V. Tsodikov** (*Universidad de Sevilla, Sevilla, Spain; **Topchiev Institute of Petrochemical Synthesis, Moscow, Russia)
Catal. Today, 128(3-4) (2007) pp. 245-250.
The local zirconium and iron arrangements of the iron-doped ZrO2-TiO2 system, prepared by sol–gel impregnation method, were studied by EXAFS spectroscopy. Only a tetragonal ZrO2 structure is located on TiO2 surface. For the iron-doped ZrO2-TiO2 system, the presence of the Fe-O-Fe species as well as and Fe-O-Zr species located on the surface/pre-surface region are shown; it seems that iron is heterogeneously distributed, forming small iron oxide nanoclusters and Fex/ZrO2 (tetragonal) spots at the catalyst surface. The photocatalytic activity of the un-doped and iron-doped binary system ZrO2-TiO2 was investigated in two kind of photoreactions: the salicylic acid photooxidation and the photocatalytic reduction of Cr(VI). Different photocatalytic behaviour has been found for the un-doped and irondoped ZrO2-TiO2 systems which have been explained in terms of the EXAFS study. This study represents an example of attempt to prepare a new potential photoactive mixed oxide system, containing two ions (Ti4+ and Zr4+) with good photocatalytic activity if it is compared with commercial TiO2 (Degusssa P25) calcined at 600°C.
STRUCTURAL PECULIARITIES OF TiO2AND Pt/TiO2CATALYSTS FOR THE PHOTOCATALYTIC OXIDATION OF AQUEOUS SOLUTION OF ACID ORANGE 7 DYE UPON ULTRAVIOLET LIGHT
G.N. Kryukova*, G.A. Zenkovets, A.A. Shutilov, M. Wilde*, K. Günter*,**, D. Fassler**, K. Richter* (*GNF e.V., Berlin-Adlershof, Germany;**GMBU e.V., Jena, Germany)
Appl. Catal. B, 71(3-4) (2007) pp. 169-176.
TiO2(anatase) with different microstructure was synthesized by thermal hydrolysis of the titanyl sulfate and studied by X-ray powder diffraction, high resolution transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The effect of titanium dioxide structure, regular or distorted, on the photocatalytic degradation of Acid Orange 7 Dye (AO7) in water upon ultraviolet light was studied. It was found that synthesized TiO2possesses a relatively high reactivity when illuminated but also show different adsorption in the dark. The relationship between these behaviors depends on the real structure of the catalysts. Catalysts with a perfect structural ordering formed after heating at temperature higher than 500°C show better photocatalytic performance. Small amount of Pt added into the TiO2structure was found to improve further the catalyst reactivity. Ptmodified titania catalysts oxidize AO7 more efficiently than P-25 Degussa TiO2. Doping effect of Pt on the structural and photocatalytic properties of the samples is discussed.
POST-METALLOCENE CATALYSTS FOR OLEFIN POLYMERISATION
K.P. Bryliakov
Russ. Chem. Rev., 76(3) (2007) pp. 253-277.
The main types of post-metallocene catalysts for olefin polymerisation based on bis(imino), bis(imino)pyridyl, bis(phenoxyimino), bis(pyrrolylimino) and other complexes of transition metals developed in the last 10–15 years and having prospects for practical use are considered. Modern views on the mechanism of action of these catalysts are discussed.
ACTIVATION OF BIS(PYRROLYLALDIMINATO) AND (SALICYLALDIMINATO) (PYRROLYLALDIMINATO)TITANIUM POLYMERIZATION CATALYSTS WITH METHYLALUMOXANE
K.P. Bryliakov, E.A. Kravtsov, L. Broomfield*, E.P. Talsi, M. Bochmann* (*University of East Anglia, Norwich, United Kingdom)
Organomet., 26(2) (2007) pp. 288-293.
Cationic intermediates formed upon activation of olefin polymerization catalyst based on bis[N-phenylpyrrolylaldiminato] titanium(IV) dichloride (L2TiCl2, I) and [N-(3-tert-butylsalicylidene)-2,3,4,5,6- pentafluoroanilinato-N′-phenylpyrrolylaldiminato] titanium(IV) dichloride (L′LTiCl2, II) with methylalumoxane (MAO) have been identified. Outer sphere ion pairs of the type [L2TiMe(S)]+[MeMAO]− and [L′LTiMe(S)]+[MeMAO]− capable of ethene polymerization have been characterized by 1H and 13C NMR spectroscopy. Unlike methyl metallocenium cations, the barrier of the first ethene insertion into the Ti-Me bonds of these species is not significantly higher than that of subsequent insertions. Surprisingly, whereas homoligated catalyst precursors L2TiCl2 in the presence of MAO are prone to ligand transfer to aluminum, under the same conditions the heteroligated system L’LTiCl2/MAO proved resistant to ligand scrambling.
ACTIVATION OF BIS(PHENOXYIMINO)ZIRCONIUM POLYMERIZATION CATALYSTS WITH METHYLALUMINOXANE AND AlMe3/[CPh3]+[B(C6F5)4]-
E.A. Kravtsov, K.P. Bryliakov, N.V. Semikolenova, V.A. Zakharov, E.P. Talsi
Organomet., 26(19) (2007) pp. 4810-4815.
The intermediates of olefin polymerization over homogeneous catalysts based on bis[N-(3-tertbutylsalicylidene) anilinato]zirconium(IV) dichloride {(LtBu)2ZrCl2} (1-tBu), bis[N-(3- methylsalicylidene)anilinato]zirconium(IV) dichloride {(LMe)2ZrCl2} (1-Me), and bis[N- (salicylidene)anilinato]zirconium(IV) dichloride {(LH)2ZrCl2} (1-H) with different activators {methylaluminoxane (MAO) and AlMe3/[CPh3]+[B(C6F5)4]-} have been studied by 1H and 13C NMR spectroscopy. Heterobinuclear ion pairs [(LtBu)2Zr(μ-Me)2AlMe2]+[Me-MAO]- (2-tBu) and [(LtBu)2Zr(μ-Me)2AlMe2]+[B(C6F5)4]- (2'-tBu) are formed upon activation of 1-tBu with MAO and AlMe3/[CPh3]+[B(C6F5)4]-, respectively. These species are the precursors of the highly active intermediates of polymerization. In contrast, the activation of 1-Me with MAO results mainly in the formation of the tight ion pair [(LMe)2ZrMe+···Me-MAO-]. This ion pair is the precursor to a poorly active intermediate of polymerization. In the catalytic systems 1-H/MAO and 1-H/AlMe3/[CPh3]+[B(C6F5)4]-, the aluminum ion pairs [LHAl(μ-Me)( μ-Cl)AlMe2]+[Me-MAO]- and [LHAl(μ-Me)(μ-Cl)AlMe2]+[B(C6F5)4]-, which were inactive in ethylene polymerization, are predominantly formed. The isomeric composition of 2'-tBu is close to that of the initial complex 1-tBu. The main route of the 1-tBu/MAO catalyst deactivation is the ligand transfer to aluminum with the formation of the complex LtBuAlMe2.
KEY INTERMEDIATES IN METALLOCENEAND POST-METALLOCENE-CATALYZED POLYMERIZATION
E.P. Talsi, K.P. Bryliakov, N.V. Semikolenova, V.A. Zakharov, M. Bochmann* (*University of East Anglia, Norwich, UK)
Kinet. Catal., 48(4) (2007) pp. 490-504.
The structures of intermediates formed upon the activation by methylaluminoxane (MAO) of a wide range of metallocene and post-metallocene catalysts of olefin polymerization were studied by 13C, 1H, and 19F NMR. For all metallocenes considered (L2ZrCl2 and L2TiCl2), under conditions similar to real polymerization conditions (Al/Zr > 200), two types of intermediates were identified in the reaction solution, namely, hetero-dinuclear ion pairs [L2M(μ-Me)2AlMe2]+[Me-MAO] (III) and zwitterionic intermediates L2MMe+←Me-Al MAO (IV) (M = Zr, Ti). The relative concentration of III increases with an increase in the Al/Zr ratio. In the post-metallocene/MAO catalytic systems, the reaction solution can be dominated either by heterodinuclear pairs of type III (bis(imino)pyridyl iron complexes) or by zwitterionic intermediates of type IV (halftitanocenes, complexes with restricted geometry). Both species III and species IV catalyze olefin polymerization. Both the species initiating polymerization, [ TiMe(S)]+[Me-MAO] , and the species responsible for chain growth, [L [ TiP]+[Me-MAO] (P is the polymer chain, and S is a solvent molecule), were characterized in the bis(phenoxyimine) titanium complex/MAO system.
FORMATION AND STRUCTURES OF CATIONIC ZIRCONIUM COMPLEXES IN TERNARY SYSTEMS Rac-(SBI)ZrX2/AlBui 3/[CPh3][B(C6F5)4] (X= Cl, Me)
K.P. Bryliakov, E.P. Talsi, N.V. Semikolenova, V.A. Zakharov, J. Brand*, C. Alonso-Moreno**, M. Bochmann** (*University of Konstanz, Konstanz, Germany; **University of East Anglia, Norwich, United Kingdom)
J. Organomet. Chem., 692(4) (2007) pp. 859-868.
Using 13C, 1H and 19F NMR spectroscopy, formation of cationic species was studied in ternary systems (SBI)ZrX2/AlBui 3/[CPh3][B(C6F5)4], where X = Cl, Me [(SBI) = rac-Me2Si(Ind)2]. In the first system (X = Cl), the ion pair [(SBI)Zr(μ-Cl)2Zr(SBI)][B(C6F5)4]2 (IV) predominates at low Al/Zr ratios (Al/Zr < 10), whereas at higher Al/Zr ratios (≥20) in the absence of monomer mainly [(SBI)Zr(μ-H)(μ-C4H7) AlBui 2] [B(C6F5)4] (V) is formed. The binuclear complex [(SBI)Zr(μ-Cl)2Zr(SBI)][B(C6F5)4]2 has been characterized crystallographically. Species V is also formed in the system X = Me at high Al/Zr ratios. In the presence of AlBui 3, IV displays activity in propylene polymerization and is the most likely precursor of the polymerizing species. Consistent mechanisms have been proposed for the reactions in these catalytic systems.
STATE OF VARIOUS STEREOREGULATING ELECTRON-DONATING COMPOUNDS IN TITANIUM-MAGNESIUM CATALYSTS FOR PROPYLENE POLYMERIZATION: A DIFFUSE REFLECTANCE IR SPECTROSCOPIC STUDY
A.G. Potapov, V.A. Zakharov, G.D. Bukatov
Kinet. Catal., 48(3) (2007) pp. 403-408.
Propylene polymerization on TiCl4/donor/MgCl2 (donor = ethyl benzoate, dibutyl phthalate, diisobutyl phthalate, diethyl 2,3-diisopropylsuccinate) supported catalysts is considered. The states of the donors in the catalysts have been investigated by diffuse reflectance IR spectroscopy. Data characterizing the distribution of the donors and the active component (TiCl4) on the support surface have been obtained. Molecular weight distribution data for polypropylene are presented. The molecular weight distribution of polypropylene depends on the location of the donor and TiCl4 molecules.
Cu(II) COMPLEXES WITH 4,6-BIS (3,5-DIMETHYL-1H-PYRAZOLE- 1-YL)PYRIMIDINE, 4-(3,5-DIMETHYL-1HPYRAZOLE- 1-YL)-6-(3,5-DIPHENYL-1HPYRAZOLE- 1-YL)PYRIMIDINE: SYNTHESIS AND CATALYTIC ACTIVITY IN ETHYLENE POLYMERIZATION REACTION
M.B. Bushuev*, V.P. Krivopalov**, N.V. Semikolenova, Yu.G. Shvedenkov*, L.A. Sheludyakova*, G.G. Moskalenko**, L.G. Lavrenova*, V.A. Zakharov, S.V. Larionov* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. J. Coord. Chem., 33(8) (2007) pp. 601-607.
The Cu(II) complexes with 4,6-bis(3,5-dimethyl- 1H-pyrazole-1-yl)pyrimidine (L1) and 4-(3,5-dimethyl-1H-pyrazole-1-yl)-6-(3,5-diphenyl- 1H-pyrazole-1-yl)pyrimidine (L2) of the composition Cu2L1Br4 and Cu2L2A4 (A = Cl, Br), respectively, were synthesized and studied by IR and magnetochemical methods. The molecular structure of the complexes is likely to be binuclear. In the presence of cocatalysts methylalumi-noxane and triisobutylaluminium, the title complexes exhibit catalytic activity in the ethylene polymerization reaction.
COBALT(II) AND COPPER(II) COMPLEXES WITH CHIRAL PYRAZOLYLQUINOLINE, A DERIVATIVE OF TERPENOID (+)-3- CARENE. CATALYTIC ACTIVITY IN ETHYLENE POLYMERIZATION REACTION
S.V. Larionov*, Z.A. Savel’eva*, N.V. Semikolenova, R.F. Klevtsova*, L.A. Glinskaya*, E.G. Boguslavskii*, V.N. Ikorskii*, V.A. Zakharov, S.A. Popov**, A.V. Tkachev** (*Nikolaev Institute of Inorganic chemistry, Novosibirsk, Russia; **Vorozhtsov Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. J. Coord. Chem., 33(5) (2007) pp. 436-448.
Coordination compounds [CoLCl2] (I), [CuLCl(NO3)] (II), CuL(NO3)2 (III), and CuLCl2 (IV) (where L is a chiral pyrazolylquinoline - a derivative of terpenoid (+)-3-carene) were synthesized. X-ray diffraction data showed that crystal structures I and II are built of mononuclear acentric molecules. In the molecule of complex I, the Co2+ ion coordinates two N atoms of bidentate cycle-forming ligand L and two Cl atoms. The coordination polyhedron of Cl2N2 is a distorted tetrahedron. For complex I, μeff = 4.50 μB, which corresponds to a high-spin configuration d7. In the molecules of II(1), II(2) (which are diastereoisomers of complex II), each Cu2+ ion coordinates two N atoms of bidentate cycle-forming ligand L, the Cl atom, and two O atoms of bidentate cyclic NO3 - ion. The ClN2O2 coordination polyhedra are tetragonal pyramids with different degrees of distortion. The structure of complex II consists of supramolecular clusters, i.e., isolated chains incorporating the molecules of II(1) and II(2). The values of μeff for II–IV correspond to the d 9 configuration. The results of EPR and IR study suggest that complex III contains the O4N2 polyhedron, whereas complex IV contains the Cl2N2 polyhedron. Complexes I and IV were found to show a high catalytic activity in ethylene polymerization reaction.
KINETIC FEATURES OF ETHYLENE POLYMERIZATION OVER SUPPORTED CATALYSTS [2,6-BIS(IMINO)PYRIDYL IRON DICHLORIDE/MAGNESIUM DICHLORIDE] WITH ALR3 AS AN ACTIVATOR
T.B. Mikenas, V.A. Zakharov, L.G. Echevskaya, M.A. Matsko
J. Polym. Sci., Part A: Polym. Chem., 45(22) (2007) pp. 5057-5066.
The effects of polymerization temperature, polymerization time, ethylene and hydrogen concentration, and effect of comonomers (hexene-1, propylene) on the activity of supported catalyst of composition LFeCl2/MgCl2- Al(i-Bu)3 (L=2,6-bis[1-(2,6-dimethylphenylimino)ethyl] pyridyl) and polymer characteristics (molecular weight (MW), molecular-weight distribution (MWD), molecular structure) have been studied. Effective activation energy of ethylene polymerization over LFeCl2/MgCl2-Al(i-Bu)3 has a value typical of supported Ziegler-Natta catalysts (11.9 kcal/mol). The polymerization reaction is of the first order with respect to monomer at the ethylene concentration >0.2 mol/L. Addition of small amounts of hydrogen (9-17%) significantly increases the activity; however, further increase in hydrogen concentration decreases the activity. The IRS and DSC analysis of PE indicates that catalyst LFeCl2/MgCl2-Al(i-Bu)3 has a very low copolymerizing ability toward propylene and hexene-1. MW and MWD of PE produced over these catalysts depend on the polymerization time, ethylene and hexene-1 concentration. The activation effect of hydrogen and other kinetic features of ethylene polymerization over supported catalysts based on the Fe (II) complexes are discussed.
ADVANCES IN THE DEVELOPMENT OF NEW CATALYSTS FOR ETHYLENE AND α-OLEFIN POLYMERIZATION
S.S. Ivanchev
Russ. Chem. Rev., 76(7) (2007) pp. 617-637.
The role of catalyst systems in the perfection of polymerisation processes and the improvement of the performance characteristics of polyethylene and other polyolefins is considered. The scope of application of post-metallocene catalysts based on transition metal α- diimine, bis(imino)pyridine and phenoxy imine complexes designed in the last decade is analysed. The structures of complexes depending on the type of ligands are described systematically. The development of research into these catalyst systems is discussed, the optimal structures as regards the activity and selectivity are mentioned, and the mechanism of their action and the prospects for industrial use are demonstrated.
ORGANIC-INORGANIC CROSS-LINKED STRUCTURES PREPARED FROM REACTIVE n-BUTYL METHACRYLATE-3- (TRIMETHOXYSILYL)PROPYL METHACRYLATE COPOLYMERS
V.N. Pavlyuchenko, O.V. Sorochinskaya, S.Ya. Khaikin, S.P. Fedorov*, E.A. Sosnov*, S.S. Pesetskii**, S.S. Ivanchev (*St. Petersburg State Technological Institute, St. Petersburg, Russia; **Belyi Institute of Mechanics of Metal-Polymer Systems, Gomel, Belarus)
Russ. J. Appl. Chem., 80(1) (2007) pp. 93-101.
The features of formation of organic-inorganic cross-linked structures prepared by copolymerization of n-butyl methacrylate with 3-(trimethoxysilyl)propyl methacrylate, followed by hydrolysis of the trimethoxysilane groups of the copolymers and condensation of the resulting silanol groups, were studied. The quantitative composition of the functional groups of the cross-linked copolymers was determined. The physicomechanical and mechanical properties of the copolymers were studied in relation to the copolymer composition and conditions of hydrolytic condensation.
STYRENE-ACRYLATE COPOLYMER PLASTISOLS WITH STABLE COLLOIDAL PROPERTIES
V.N. Pavlyuchenko, O.N. Primachenko, S.S. Ivanchev
Polymer Sci., ser. A, 49(10) (2007) pp. 1086-1092.
Methods for the synthesis of emulsionpolymerized styrene–methyl methacrylate– methacrylic acid copolymers with different compositions and structures are proposed. Stable plastisols are obtained from these copolymers and phthalate plasticizers. Factors that affect the colloidal stability and rheological properties of the plastisols were studied. These are the polymer particle size, the type of surfactants used in emulsion copolymerization, the distribution of methacrylic acid units over the latex particle volume (uniform or gradient, with concentration rising from the particle center to periphery), the degree of carboxyl group neutralization with a base, and the nature of plasticizers. The plastisols obtained are characterized by a pseudoplastic flow. However, as the degree of carboxyl group neutralization in the copolymers is increased, the rheological properties of the plastisols approach those of Newtonian liquids.
CATALYTIC ACTIVITY OF SYSTEMS BASED ON TITANIUM BIS(PHENOXY IMINE) COMPLEXES: EFFECT OF THE LIGAND STRUCTURE
M.Yu. Malinskaya, N.I. Ivancheva, I.I. Oleinik*, G.A. Tolstikov*, S.S. Ivanchev (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. J. Appl. Chem., 80(9) (2007) pp. 1515-1522.
Polymerization of ethylene at 30–70°C in the presence of catalytic systems based on titanium bis(phenoxy imine) complexes of various structures, activated with methylalumoxane, was studied. An attempt was made to systematize the effect of substituents in ligands, to find correlations, to account for the results obtained, and to reveal conditions under which the reaction occurs by the living polymerization mechanism. Some properties and structural features of the polyethylenes obtained were determined.
FEATURES OF SELF-IMMOBILIZATION OF TITANIUM PHENOXYIMINE COMPLEXES IN ETHYLENE POLYMERIZATION
N.I. Ivancheva, M.Yu. Malinskaya, I.I. Oleinik*, S.Ya. Khaikin, G.A. Tolstikov* (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Doklady Phys. Chem., 417(1-3) (2007) pp. 301-304.
Kinetic features of self-immobilization of catalytic complex over polyethylene obtained and kinetics of ethylene polymerization are illustrated by the example of methylaluminoxane-activated titanium bis(phenoxy imine) complexes modified with oxyallylic groups. The activity of catalyst selfimmobilized over polyethylene is for the first time studied and compared with similar by composition homogeneous catalyst.
ETHYLENE POLYMERIZATION ON TITANIUM PHENOXYIMINE COMPLEXES WITH DIFFERENT STRUCTURES
N.I. Ivancheva, M.Yu. Malinskaya, S.S. Ivanchev, I.I. Oleinik*, A.I. Kochnev*, G.A. Tolstikov* (*Vorozhtsov Institute of Organic Chemistry, Novosibirsk, Russia)
Kinet. Catal., 48(6) (2007) pp. 829-834.
The kinetics of ethylene polymerization in the presence of catalytic systems based on methylaluminoxane-activated titanium bis(phenoxyimine) complexes with different structures has been investigated in the temperature range 30-70°C. The structures of the complexes have different substituents at the imine nitrogen atom and in the phenoxy group in the ligand, which affect the activity of the system and the molecular weight of polyethylene resulting from polymerization over at least 1 h. The polymerization kinetics is most sensitive to the structure of the substituent at the imine nitrogen atom and to bulky substituents in the ortho position of the phenoxy group. The results obtained are explained. An attempt is made to classify the influence of the substituents in the ligands. Process conditions ensuring living polymerization have been found. The physicochemical properties and structural features of the polyethylenes obtained have been determined.
A NEW POLYMERIC SILICONE HYDROGEL FOR MEDICAL APPLICATIONS: SYNTHESIS AND PROPERTIES
N.A. Chekina, V.N. Pavlyuchenko, V.F. Danilichev*, N.A. Ushakov*, S.A. Novikov*, S.S. Ivanchev (*Military Medical Academy, St. Petersburg, Russia)
Polym. Advanced Technol., 17(11-12) (2006) pp. 872-877.
A novel silicone hydrogel polymeric material is developed. The preparation method is based on sequential interpenetrating network synthesis. A silicone network is obtained by the interaction between two siloxane oligomers comprising hydride and vinyl functional groups. A hydrophilic network is prepared by radical copolymerization of hydrophilic monomers (N-vinyl pyrrolidone, N,N-dimethylacrylamide) and crosslinking agent (ethylene glycol dimethacrylate). In the hydrated state the developed material has high mechanical properties, transparency, hydrophilicity, oxygen and water permeability. The developed new technology affords obtaining a silicone hydrogel material with a good wettability without additional chemical or plasma surface treatment.
EFFECT OF HYDROGEN BONDS ON ORIENTATIONAL ORDER IN LIQUID-CRYSTALLINE POLYMERS
E.B. Barmatov*, M.V. Barmatova (*Novosibirsk Technological Center Shlumberger, Novosibirsk, Russia)
Polymer Sci., ser. B, 49(9-10) (2007) pp. 222-223.
The orientational behavior of nematic LC copolymers (4-{[6-(acryloyloxy)hexanoyl]oxy}phenyl-4- propoxybenzoate)-co-(4-(6-acryloyloxypropyl-1-oxy) benzoic acid) in a magnetic field has been studied by H2 NMR spectroscopy. An increase in the content of carboxyl groups in the copolymer leads to an appreciable growth of the orientational order parameter S-zz.
OPTICALLY ISOTROPIC MESOPHASE IN COMB-SHAPED COPOLYMERS WITH SIDE MESOGENIC GROUPS
E.B. Barmatov*, D.A. Pebalk**, M.V. Barmatova (*Novosibirsk Technological Center Shlumberger, Novosibirsk, Russia; **Moscow Lomonosov State University, Moscow, Russia)
Polymer Sci., ser. A, 49(2) (2007) pp. 148-157.
Two series of comb-shaped copolymers poly(4- (4-cyanobiphenyl-4'-yloxy)butyl acrylate)-co-(4-(6- acryloyloxyhexyl-1-oxy)isophthalic acid)) and poly(4- (6-acryloyloxyhexyl-1-oxy)benzoic acid)-co-(acrylic acid)) have been prepared by free-radical copolymerization, and their phase diagrams have been constructed. Formation of the optically isotropic phase characterized by the absence of birefringence and high optical activity has been demonstrated for a number of copolymers. At the same time, the DSC curves of these compounds show a well-defined phase transition with the heat of melting equal to 2–5 J/g. Specific features of hydrogen bonding in the copolymers have been studied by IR spectroscopy. It has been speculated that there is correlation between microphase separation between hydrophobic and hydrophilic units in the copolymers and formation of the optically isotropic mesophase.
NEW POLYMER LIQUID-CRYSTALLINE CdS NANOCOMPOSITES FORMING A CHIRAL NEMATIC PHASE
E.B. Barmatov*, D.A. Pebalk**, M.V. Barmatova (*Novosibirsk Technological Center Shlumberger, Novosibirsk, Russia; **Moscow Lomonosov State University, Moscow, Russia)
Polymer Sci., ser. B, 49(1-2) (2007) pp. 47-50.
A new approach has been developed for the design of liquid-crystalline polymer nanocomposites combining the unique properties of polymer cholesterics and quantum dots of CdS.
THE EFFECT OF SILVER NANOPARTICLES ON THE PHASE STATE OF COMB-SHAPED LIQUID CRYSTALLINE POLYMERS WITH CYANOBIPHENYL MESOGENIC GROUPS
E.B. Barmatov*, A.S. Medvedev*, D.A. Pebalk**, M.V. Barmatova, N.A. Nikonorova***, S.B. Zezin***, V.P. Shibaev*** (*Novosibirsk Technological Center Shlumberger, Novosibirsk, Russia; **Moscow Lomonosov State University, Moscow, Russia; ***Institute of Macromolecular Compounds, St. Petersburg, Russia)
Polymer Sci., ser. A, 48(7) (2007) pp. 665-675.
A new approach is proposed for the preparation of a new class of hybrid polymer systems based on comb-shaped LC polymers with cyanobiphenyl mesogenic groups and silver nanoparticles with dimensions ranging from 5 to 54 nm. A correlation between copolymer composition and dimensions of the formed nanoparticles is established. As the concentration of nanoparticles in LC copolymer is increased, the resultant glass transition temperature increases, and the temperature interval of the existence of LC phase is reduced. This behavior is related to the adsorption of cyanobiphenyl and carboxylic polymer groups on the surface of silver nanoparticles. In this case, the conductivity and dielectric permittivity of the composites are also increased.
POTENTIAL OF CATALYTIC TECHNOLOGIES
V.N. Parmon, A.S. Noskov
Catal. Ind., 4 (2007) pp. 3-18.
The paper considers current trends in the area of catalytic technologies in Russian chemical and petrochemical industries caused by the ever increasing demands for catalysts and catalytic technologies for fine processing of hydrocarbons into valuable products, polymers, aromatic compounds, carbon nanostructured materials and other high-tech materials. The discussion is exemplified with developments of the Boreskov Institute of Catalysis in the framework of Russian State Innovative Projects. The Projects are aimed at development and commercialization of catalysts for synthesis of motor fuels, for large-scale production of polyolefins. Among recent BIC’s advances are the technologies for processing of oil associated gases into aromatic compounds, for hydrogenation of plant oils over palladium catalysts, for oxidation of benzene to phenol with nitrous oxide, for synthesis of formic and nicotinic acids, for gas cleaning from hydrogen sulfide by oxidation into elemental sulfur and many other ecologically friendly technologies. In conclusion, the authors assess the Russian market potentials regarding large-scale catalytic technologies for oil processing and petrochemistry
FIXED BED REACTORS WITH GRADIENT CATALYST
V.M. Khanaev, E.S. Borisova, A.S. Noskov
In “Chemical Engineering Research Trends”, Ed. Leon P. Berton , Nova Publishers, 2007, Chapter 3, pp. 127-201.
High-energy catalytic processes operated in fixed bed reactors are widely used in many fields of Chemical Engineering, so the improvement of specific intensities of such processes to minimize the equipment size and related capital cost, to enhance the reliability is of great importance. The specific features of such processes are reactant concentration gradients through the bed length which may cause considerable temperature gradients in exo-endothermic reactions; therefore, the catalysts used for the existing and innovative high-energy catalytic processes must meet severe requirements. The catalytic processes in fixed bed reactors are rather complicated and usually include the chemical reactions, the processes of mass and heat transfer and reactant adsorption/desorption. As a result, a specially organized catalytic fixed bed with non-uniform properties (gradient catalysts) may appear more appropriate in some cases than the uniform one. At present, the ideas of gradient catalysts are used for creation the new type of afterburning catalysts, for microchannel reactors. In the theoretical investigation the attention is being increasingly focused on the complex approach based on the optimization of heat- and mass transfer and of the activity of the whole catalyst bed through the optimal bed packing, granule shape, distribution of the active component, heat conductivity etc., i.e. through creation of some optimal gradient medium for conducting the catalytic process. Fundamentals for optimization of the spatial bed structure, in particular for optimization of the active component distribution through the bed length, are developed intensively with regard to synthesis of new materials and creation of new methods for arranging reaction beds (for example, in microchannel reactors). The authors of the present paper are the first who proposed to use the variational approach for solving these problems, so they theoretically formulated the problem of a catalytic process optimization by means of nonuniform spatial active sites distribution and obtained the analytic solutions for several cases. In the present paper, the following points will be discussed:
CONVERSION OF CHEMICAL REACTION ENERGY INTO USEFUL WORK IN THE VAN'T HOFF EQUILIBRIUM BOX
N.M. Bazhin*, V.N. Parmon (*Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia)
J. Chem. Educ., 84(6) (2007) pp. 1053-1055.
The production of useful work by means of the ideal "van't Hoff equilibrium box" is considered in detail. It is shown that useful work arises according to the scheme “reaction energy → heat → useful work” without violation of the second law of thermodynamics, even at constant temperature, using the heat evolved by a reaction. Van't Hoff equilibrium box divided in two parts can produce simultaneously heat (in volume 100 % from theoretical one) and useful work (in volume 100 % from theoretical one) without violation of the first law of thermodynamics.
DIRECT CATALYTIC OXIDATION OF METHANE TO FORMALDEHYDE: NEW INVESTIGATION OPPORTUNITIES PROVIDED BY AN IMPROVED FLOW CIRCULATION METHOD
I.I. Bobrova, N.N. Bobrov, L.G. Simonova, V.N. Parmon
Kinet. Catal., 48(5) (2007) pp. 676-692.
An improved flow circulation reactor with reaction mixture quenching was used to study the direct oxidation of methane to formaldehyde at 600-770°C, a CH4/O2 volume ratio of 1 : 1 in the starting mixture, and gas mixture flow rates of 0.4-2.0 l/h. It was found that, in the presence of a surface containing SiO2 (quartz reactor walls, the surface of silica packing materials, or the surface of SiO2 as a catalyst constituent), the process occurred by a heterogeneous–homogeneous mechanism with chain continuation in the volume of a gas phase. The process was controlled by the size and shape of the free reaction volume, the contact surface area, and the residence time of a mixture in the reaction volume. The introduction of typical oxidation catalysts containing, for example, Pt or V2O5 as an active component along with SiO2 resulted in a decrease in the yield of and selectivity for formaldehyde.
MICROCHANNEL CATALYTIC SYSTEMS FOR HYDROGEN ENERGETICS
L.L. Makarshin, V.N. Parmon
Russ. J. General Chem., 77(4) (2007) pp. 676-684.
The concept of hydrogen energetics envisages economically reasonable hydrogen production from various organic compounds in stationary and mobile devices of low and medium performance, called “fuel processors”. Fuel processors with a high specific performance in hydrogen can be developed with the aid of microchannel catalytic systems. The paper considers the present situation with microchannel catalytic reactors for fuel processors.
OVERALL PERFORMANCE OF THE CATALYST IN A MICROREACTOR FOR THE METHANE PARTIAL OXIDATION
L.L. Makarshin, D.V. Andreev, S.N. Pavlova, V.A. Sadykov, V.V. Privezentsev*, A.V. Gulevich*, V.A. Sobyanin, V.N. Parmon (*SSCRF - Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia)
Intern. Sci. J. Alternative Energy Ecol., 2 (2007) pp. 132-134.
The goal of this work is investigation of partial methane oxidation (POM) for syngas production in the microchannel system. The features of such systems are high specific productivity which allows to use their in various mobile devices. The method of firm catalyst deposition on the metal microchannel plates functioning at 900°C was developed which permits a repeated thermocycling of the plates. At gas hourly space velocity 700000 h-1 the methane conversion was 90 % and carbon monoxide selectivity was 60 %. Hydrogen production was proportional to number of the microchannel plates loaded in the microreactor and was 34 l/h for one plate and 380 l/h for ten plates. Specific hydrogen production relative to the microreactor’s volume was 1.7·104 l/(h·dm3). It is found that thermal load distributes nonuniformly along the microchannel plate due to the POM reaction exothermicity which results in corrosion of the front edge (about 1 mm) of the microchannel plate. Additional experiments and theoretical calculations have shown that in the course of the POM process in front side of the microchannel plate the total oxidation of methane occurs following high heat evolution and H2O and CO2 formation. On the rest side of the plate endothermic steam and dry reforming of methane occurs with CO and H2 formation.
EFFECT OF THE MICROCHANNEL PLATE DESIGN ON THE CAPACITY OF METHANOL STEAM REFORMERS
L.L. Makarshin, D.V. Andreev, A.G. Gribovskii, P.M. Dutov*, R.M. Khantakov*, V.N. Parmon (*Novosibirsk State University, Novosibirsk, Russia)
Kinet. Catal., 48(5) (2007) pp. 765-771.
Methanol steam reforming in microreactors is considered, and the effects of the microreactor geometry (cylindrical and rectangular) and microchannel plate (MCP) design on the hydrogen capacity of the microreactor is analyzed. The MCPs were made from aluminum foil, stainless steel, and foamed nickel by laser engraving, electrochemical etching, and pressing. The amount of catalyst powder (CuO/ZnO = 40 : 60 mol/mol) fixed on one MCP was 0.04–2.5 g. The specific hydrogen capacity (Uw) of the cylindrical microreactor is more than 3 times as high as the Uw of the rectangular microreactor and is 6 times as high as the Uw of a conventional fixed-bed catalytic reactor. This gain in hydrogen capacity is due to the more efficient use of the catalyst in the microreactors. The MCP design, which determines the residence time of the reactants in the microreactor, also has a significant effect on the capacity of the microreactor.
INFLUENCE OF THE MICROCHANNEL PLATES DESIGN ON THE EFFICIENCY OF THE METHANOL STEAM REFORMING IN MICROREACTORS
L.L. Makarshin, D.V. Andreev, A.G. Gribovskii, V.N. Parmon
Intern. J. Hydrogen Energy, 32(16) (2007) pp. 3864-3869.
The reaction of methanol steam reforming in microchannel microreactors was studied and the effect of catalyst structure and microreactor design on the reaction rate constant of methanol steam reforming was elucidated. Three types of microreactors were studied - rectangular, cylindrical and tubular with fixed catalyst bed. To analyze the experimental data a simple kinetic model with power-law rate equation with the first reaction order for the methanol was used. It was shown that the value of reaction rate constant and hydrogen production depends on structure of the catalyst loaded into the reaction volume. The highest reaction rate constant and specific hydrogen production equal 8.11/(hgcat)was observed for the rectangular microreactor, with two metal plates with deposited catalyst. The cylindrical microreactors produced 6.21/(hgcat) of hydrogen. The tubular microreactor exhibited the lowest reaction rate constant and specific hydrogen production equal 4.91/(hgcat). This fact seems to be associated with the temperature gradient in the reactor due to the endothermic reaction of the methanol steam reforming. Using the Arrhenius equation the temperature gradient in the reaction volume was estimated - 6.7 and 13.6 K for the cylindrical and tubular microreactors, respectively. These results agreed with heat balance calculations.
COBALT FISCHER-TROPSCH SYNTHESIS: DEACTIVATION BY OXIDATION?
J. van de Loosdrecht*, B.S. Balzhinimaev, J.-A. Dalmon**, J.W. Niemantsverdriet***, S.V. Tsybulya, A.M. Saib*, P.J. van Berge*, J.L. Visagie* (*Sasol Technology Ltd, South Africa; **Institute de Recerches sur la Catalyse, Villeurbanne Cedex, France; ***Eindhoven University of Technology, The Netherlands)
Catal. Today, 123(1-4) (2007) 293-302.
Cobalt catalysts as used in the Fischer-Tropsch synthesis (FTS) are relatively expensive (as compared to iron) and need to have a high metal dispersion and long life to be able to offer a good balance between cost and performance. The oxidation of nano-sized metallic cobalt to cobalt oxide during Fischer-Tropsch synthesis has long been postulated as a major deactivation mechanism. However, to date there is no consistent picture. This paper presents an extensive overview of the literature on this topic of deactivation by means of oxidation for unsupported as well as silica-, alumina- and titania-supported cobalt catalysts. Furthermore, it presents results on the deactivation of an industrial Co/Al2O3 catalyst as obtained by pseudo in situ X-ray diffraction, magnetic measurements and X-ray absorption near-edge spectroscopy. These analyses were performed to study the oxidation state of spent industrial Co/Al2O3 catalyst samples withdrawn from a slurry reactor operating under realistic FTS conditions, and it was concluded that oxidation can be ruled out as a major deactivation mechanism. Finally, these data together with all relevant literature were used to create a common view on the oxidation behaviour of cobalt during FTS. The apparent discrepancies in literature on the oxidation behaviour of cobalt are most likely due to the lack of direct characterisation of the cobalt oxidation state and due to the comparison of catalysts with varying cobalt crystallites compared at different reactor partial pressures of hydrogen and water (PH2O/PH2). It was shown that the oxidation of cobalt can be prevented by selecting the correct combination of the reactor partial pressures of hydrogen and water (PH2O/PH2) and the cobalt crystallite size.
MODELING OF A HEAT-COUPLED CATALYTIC REACTOR WITH CO-CURRENT OXIDATION AND CONVERSION FLOWS
V.A. Kirillov, S.I. Fadeev*, N.A. Kuzin*, A.B. Shigarov (*Sobolev Institute of Mathematics, Novosibirsk, Russia)
Chem. Eng. J., 134(1-3) (2007) pp. 131-137.
Mathematical model and numerical method are developed to analyze the operation of a coupled methane steam reformer. The reformer operates in cocurrent mode of endothermic (steam reforming) and exothermic (fuel oxidation) departments. The exhaust anode gas of a fuel-cell battery containing hydrogen is used as fuel. Two-dimensional, two-temperature mathematical model of monolith is used to describe processes in exothermic and endothermic departments of the reformer. Calculation results were compared with experiments. The agreement between the modeling and the experimental results is rather good. The model analysis points out that the considered reactor design has high parametric sensitivity, there is a probability of arisen of a hysteresis with points of ignition and extinction.
ANALYSIS OF STABILITY OF THE INTERPHASE FRONT WITH EVAPORATION AND EXOTHERMIC REACTION IN THE POROUS CATALYST SLAB
A.B. Shigarov, A.A. Bocharov, V.A. Kirillov
Chem. Eng. Sci., 62(17) (2007) pp. 4770-4779.
Using a two-dimensional mathematical model and a number of simplifying assumptions, the analytical (linear) analysis of stability of the reaction– evaporation front inside the half-wetted porous catalyst slab was made. Based on the obtained spectral equation, the effect of different parameters on possible types of instability was studied.
n-HEXANE SKELETAL ISOMERIZATION OVER SULFATED ZIRCONIA CATALYSTS WITH DIFFERENT LEWIS ACIDITY
G.G. Volkova, S.I. Reshetnikov, L.N. Shkuratova, A.A. Budneva, E.A. Paukshtis
Chem. Eng. J., 134(1-3) (2007) pp. 106-110.
The n-hexane skeletal isomerization over Pt/SO4 2−/Al2O3/ZrO2 catalysts with different density of Lewis acid sites has been studied in a fixed-bed reactor. The acidity of the catalysts was characterized by FTIR spectroscopy of low temperature CO adsorption. The calculation of the rate constants, characterizing the catalyst activity and selectivity was performed on the base of mathematical model of plug flow reactor. It was shown that the rate of hexane isomerization is mainly determined by the density of Lewis acid sites on the surface of sulfated zirconia catalysts: rate constant of n-hexane isomerization for catalyst with Lewis acidity 250 μmol g−1 is four-fold as that for catalyst with concentration of Lewis acid sites 150 μmol g−1 and the rate constant of desired product (2,2-dimethylbutane) formation is also higher by two times.
UNSTEADY CATALYTIC PROCESSES AND SORPTION-CATALYTIC TECHNOLOGIES
A.N. Zagoruiko
Russ. Chem. Rev., 76(7) (2007) pp. 639-654.
Catalytic processes that occur under conditions of the targeted unsteady state of the catalyst are considered. The highest efficiency of catalytic processes was found to be ensured by a controlled combination of thermal non-stationarity and unsteady composition of the catalyst surface. The processes based on this principle are analysed, in particular, catalytic selective reduction of nitrogen oxides, deep oxidation of volatile organic impurities, production of sulfur by the Claus process and by hydrogen sulfide decomposition, oxidation of sulfur dioxide, methane steam reforming and anaerobic combustion, selective oxidation of hydrocarbons, etc.
SORPTION-ENHANCED STEAM REFORMING OF HYDROCARBONS WITH AUTOTHERMAL SORBENT REGENERATION IN A MOVING HEAT WAVE OF A CATALYTIC COMBUSTION REACTION
A.N. Zagoruiko, A.G. Okunev
React. Kinet. Catal. Lett., 91(2) (2007) pp. 315-324.
A novel technological concept of sorptionenhanced steam reforming of hydrocarbons is suggested. The peculiarity of the concept is the autothermal regeneration of the carbon dioxide scavenger in the moving super-adiabatic heat wave of an exothermic catalytic combustion reaction performed directly inside the adsorption-catalytic bed. The capability and high efficiency of the proposed technological approach are confirmed by process simulation. The approach proposed is shown to open a way for the creation of an inexpensive, reliable and energy-saving adiabatic packed bed methane processors of unlimited processing capacity.
SIMULATION OF SELECTIVE REACTIONS’ PERFORMANCE IN TRANSIENT REGIMES WITH PERIODICAL SEPARATE FEEDING OF REAGENTS. CASE STUDY: PROPANE OXIDATIVE DEHYDROGENATION IN ADIABATIC V–Ti CATALYST BED
A.N. Zagoruiko
Chem. Eng. J., 134(1-3) (2007) pp. 117-122.
The model simulation study has shown that the anaerobic process of oxidative dehydrogenation of propane under periodic alteration of feeding between propane and air may be realized in adiabatic catalyst beds in stable continuous cyclic mode in two-reactor scheme. In case of appropriate choice of process parameters (cycle duration and residence times), the process appears to be autothermal, i.e. it does not require any inlet gas preheating for stable operation. Compared to similar steady-state adiabatic process, the proposed process is characterized with much lower maximum catalyst temperatures, giving the way to process pure propane without diluting it with inert gases, thus simplifying downstream procedure of product separation. Predicted propylene yield is competitive with one for the steady-state adiabatic process, while sufficient technological benefits of the new technology are expected (decrease of energy consumption and minimization of heat-exchange environment, simplification of product separation procedure, process safety improvement, suppression of coke formation and efficient coke incineration). Notably, the proposed process is characterized with much more degrees of freedom available for further development and optimization than conventional steady-state technologies.
KINETIC INSTABILITIES AND INTRA-THREAD DIFFUSION LIMITATIONS IN CO OXIDATION REACTION AT Pt/FIBER-GLASS CATALYSTS
A.N. Zagoruiko, S.A. Veniaminov, I.N. Veniaminova, B.S. Bal’zhinimaev
Chem. Eng. J., 134(1-3) (2007) pp. 111-116.
Experimental and mathematical simulation studies of CO oxidation reaction at Pt-based glass-fiber catalyst showed that reaction phenomena in fabric and threads of woven glass-fiber catalysts is rather complicated by transfer limitations, which may impose especially valuable influence on reactions with strongly non-linear kinetics. Such limitations are related to extra-thread and intra-thread heat and mass transfer. Additionally, in thin beds, consisting of one or few layers of woven catalyst, the significant role may be played by experimentally confirmed transient oscillations between CSTR and plug-flow regimes, therefore, the axial heat and mass dispersion is an important transfer factor for such beds as well. Mathematical modelling of phenomena inside the catalyst thread on the basis of elaborated kinetic model showed possibility of existence of steady-state multiplicity as a self-sufficient result of intra-thread transfer limitations. In general, observed reaction rates at the catalyst thread and location of multiplicity region may depend upon many factors (thread diameter and porosity, surface CO concentration and temperature and even choice of reaction media balance gas), which should be taken into account for correct formulation of lab experimental procedure, interpretation of experimental data and process scale-up.
BENZENE HYDROGENATION IN THE THIOPHENE PRESENCE OVER THE SULFIDE Ni-Mo/γ-Al2O3 CATALYST UNDER PERIODIC OPERATION: KINETICS AND PROCESS MODELLING
S.I. Reshetnikov, E.A. Ivanov, A.N. Startsev
Chem. Eng. J., 134(1-3) (2007) pp. 100-105.
An unsteady-state kinetic model of both benzene hydrogenation (HDA) and thiophene hydrogenolysis (HDS) on the sulfide hydrotreating catalyst Ni-Mo/Al2O3 has been developed. The model adequately describes experimental data obtained at the pressure 2 MPa, temperature 573 K and at various contact times and ratios of benzene/thiophene. The model is based on the assumption that the catalyst surface contains only one type of active sites, i.e., Ni atoms in the sulfide bimetallic species, which are responsible for both hydrogenolysis and hydrogenation reactions. On the base of the kinetic model, a theoretical analysis of the reactor performance under unsteady state conditions was carried out. The unsteady state conditions on the catalyst surface are supposed to be created by forced oscillations of thiophene concentration in the reactor inlet (periodic operation of reactor). The influence of various parameters like cycle split, length of period of forced oscillations in the reactor was investigated with respect to the conversion of the benzene. It is shown that for periodic reactor operation an average conversion was up to several times higher than a steady state value.
SYNGAS FORMATION FROM GASOLINE IN ADIABATIC REACTOR: THERMODYNAMIC APPROACH AND EXPERIMENTAL OBSERVATIONS
L.N. Bobrova, V.M. Korotkikh, V.A. Sadykov, V.N. Parmon
Chem. Eng. J., 134(1-3) (2007) pp. 145-152.
To make viable the large-scale use, generation of hydrogen locally from the petroleum-derived fuels such as gasoline is an attractive way because of the existing production, distribution, and retailing infrastructure. The present work is centered on the syngas formation from gasoline. The thermodynamic equilibrium restrictions on the gasoline reforming process in comparison with isooctane and methane are discussed on the basis of multi-component calculations. To perform the thermodynamic modelling, the real fuel containing 191 hydrocarbon species was specified as an equilibrium distribution of 29 close-cut fractions C3–C10 with well-defined properties. The thermodynamic predictions are in a good correlation with the experimental data obtained in a nearly adiabatic monolith reactor.
HYDROGEN-RICH GAS PRODUCTION FROM GASOLINE IN A SHORT CONTACT TIME CATALYTIC REACTOR
L.N. Bobrova, I.A. Zolotarsky, V.A. Sadykov, V.A. Sobyanin
Int. J. Hydrogen Energy, 32(16) (2007) pp. 3698–3704.
Presented is a study of hydrogen-rich gas generation by selective catalytic oxidation of gasoline in a nearly adiabatic monolith reactor. Experiments were conducted using a gasoline mixture containing 191 hydrocarbon species, while corresponding thermodynamic models employed a surrogate mixture of 29 organics with well-defined properties. Based on the data obtained, it was demonstrated that a nearly equilibrium synthesis gas could be produced using catalytic monoliths. Also discussed are problems encountered with a short contact time reactor operating at a pilot-scale, issues that are largely independent of the catalysts employed. It was found that this particular reactor design is prone to prereformation of the fuel prior to catalytic reaction. In addition, the breakthrough of the feed mixture was found to arise near the reactor wall under certain circumstances. Feed composition, superficial velocity, and various reactor design factors were all found to affect these phenomena.
TRANSIENT BEHAVIOR OF THE METHANE PARTIAL OXIDATION IN A SHORT CONTACT TIME REACTOR: MODELING ON THE BASE OF CATALYST DETAILED CHEMISTRY
N.V. Vernikovskaya, L.N. Bobrova, L.G. Pinaeva, V.A. Sadykov, I.A. Zolotarskii, V.A. Sobyanin*,**, I. Buyakou***, V. Kalinin***, S. Zhdanok*** (*The Boreskov Institute of Catalysis, Novosibirsk Russia; **Novosibirsk State University, Novosibirsk Russia; ***Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus, Minsk, Belarus)
Chem. Eng. J., 134(1-3) (2007) pp. 180-189.
The objective of the paper is a numerical study of the partial oxidation of methane to synthesis gas in a monolith reactor with Pt/Ce-Zr-La catalyst. A dynamic one-dimensional two-phase reactor model of the processes with accounting for both transport limitations in the boundary layer of a fluid near the catalyst surface and detailed molecular unsteady-state kinetic model for surface reactions have been developed and verified with the transient experiments data. The mathematical model was used to explain a transient behavior of the process in the monolith reactor during start-up (ignition). Also studied is the influence on the process dynamics such parameters as linear velocity, equivalent diameter of triangular channel and effective thermal conductivity of the monolith. It was found that higher linear velocity and equivalent channel diameter as well as the worse axial conductivity of solid phase favor decreasing a time delay in syngas production in the Pt/Ce-Zr-La/α-Al2O3 honeycomb monolith with a triangular shape channels.
OPTIMUM DIMENSIONS OF SHAPED STEAM REFORMING CATALYSTS
A.P. Kagyrmanova, I.A. Zolotarskii, E.I. Smirnov, N.V. Vernikovskaya
Chem. Eng. J., 134(1-3) (2007) pp. 228-234.
In this paper, a theoretical optimization of shaped catalyst dimensions with technologically imposed constraints is presented for operating conditions of a typical methanol reformer. A comprehensive twodimensional mathematical model of a single reformer tube containing physically sound correlations for heat transfer parameters of holed catalyst particles is used. Three-hole pellets and Raschig rings were used as examples. A general conclusion is made that holed steam reforming catalysts should have maximum catalyst height and minimum diameter determined by requirements of uniform catalyst packing.
COMPACT REACTOR FOR WATER GAS SHIFT REACTION OVER THERMALCONDUCTING CATALYSTS
N.A. Baronskaya, T.P. Minyukova, A.G. Sipatrov, M.P. Demeshkina, A.A. Khassin, S.V. Dimov*, S.P. Kozlov*, V.V. Kuznetsov*, V.Ya. Terentiev**, A.P. Khristolyubov**, O.F. Brizitskiy**, T.M. Yurieva (*Kutateladze Institute of Thermophysics, Novosibirsk, Russia; **Russian Institute for Experimental Physics (VNIIEF), Sarov, Russia)
Chem. Eng. J., 134(1-3) (2007) pp. 195-199.
Thermal conductive catalyst plates (TCP) for compact WGSR reactors were prepared and studied. High thermal conductivity of 2.5–5 W (m K)−1 can be achieved, while the effective catalytic activity of TCP is even higher than that of the commercial size catalyst grains. TCP can be efficiently used for temperature sensitive exothermic reactions in compact apparatuses with controlled temperature profile. Using the TCP reactor WGSR of the fuel gas containing 12% of CO down to 1% of residual CO can be performed in one stage at GSHV of above 6000 h-−1. The TCP shape and the way of arrangement are important for the reactor performance and should be in the focus of future studies.
PERMEABLE COMPOSITE MATERIAL FOR COMPACT APPARATUS FOR HYDROGENRICH GASES DEEP CLEANING FROM CO
T.P. Minyukova, I.Sh. Itenberg, A.A. Khassin, A.G. Sipatrov, E.V. Dokuchits, V.Ya. Terent’ev*, A.P. Khristolyubov*, O.F. Brizitskii*, T.M. Yurieva (*Russian Institute for Experimental Physics (VNIIEF), Sarov, Russia)
Chem. Eng. J., 134(1-3) (2007) pp. 235-238.
In order to provide a wide application of the proton exchange membrane fuel cell (PEMFC) technology, reduce cost and improve characteristics of PEMFC-based power plants, it is necessary to create a compact and economic apparatus for deep cleaning of converted fuel from carbon monoxide. The obstacle of preferential CO hydrogenation is the presence of about 20 vol.% of CO2 and the same amount of H2O along with 1 vol.% of CO. The compact apparatus for deep purification from CO can be only created basing on the highly active (providing 10–20 ppm CO in the outlet gas at GHSV above 6000 h−1) and selective catalyst (at least 30% of CH4 and higher hydrocarbons is to be formed by CO hydrogenation). The process of preferential CO hydrogenation over the nickelchromium catalyst is studied, which was found earlier to be efficient in the CO hydrogenation over fine catalyst fraction: outlet CO content below 20 ppm and the selectivity not less than 0.3 at GHSV above 6000 h−1. The effect of the catalyst grain size on the CO hydrogenation selectivity is reported and the possibility of using permeable composite materials for weakening the intraparticle diffusion constrains and for efficient performing the reaction under the study close to the kinetic region is considered.
MATHEMATICAL MODELING AND EXPERIMENTAL STUDY OF HIGH-PRESSURE ETHYLENE POLYMERIZATION REACTORS
S.S. Ivanchev, M.V. Goncharenko*, Yu.N. Kondratiev*, A.M. Saveliev*, A.E. Sofiev* (*Central R&D Institute for Complex Automation, Moscow, Russia)
Chem. Eng. J., 134(1-3) (2007) pp. 175-179.
Mathematical models and experimental data are discussed for high-pressure ethylene polymerizations in stirred autoclaves and tubular reactors. The models are based on free radical mechanism of ethylene polymerization using material and energy balance equations as well as impact balance (for tubular reactors). A stirred autoclave reactor is modeled taking into account mixing modes in the reactor on the basis of the segregation approach. The developed mathematical model was used to study the stability of stirred autoclave reactor and determine the range of the process parameters corresponding to their sustainable functioning.
AUTOWAVE PROCESSES IN A HETEROGENEOUS MEDIUM WITH CHEMICAL REACTIONS IN A GASEOUS PHASE AND IN A CATALYST BED
A.P. Gerasev
Theor. Found. Chem. Eng., 41(2) (2007) pp. 116-123.
A mathematical model is constructed for autowave processes in a heterogeneous medium with chemical reactions in a gaseous phase and in a catalyst bed. The model accounts for the changes in the interphase heat and mass transfer and thermal conductivity coefficients of the catalyst bed as a function of the system parameters. The phase trajectories of the dynamic system are investigated using qualitative and numerical analyses, and an effective technique for searching for a physically comprehensive autowave solution of the problem is proposed. The mathematical model of hybrid autowaves is tested in a cycle of numerical calculations, and the influence of the system parameters on the main technological characteristics of the autowave processes is analyzed.
AUTOWAVES IN A HETEROGENEOUS MEDIUM WITH A CATALYTIC REACTION AND HEAT AND MASS TRANSFER
A.P. Gerasev
Combust., Explosion, Shock Waves, 43(2) (2007) pp. 162-169.
A mathematical model is developed to describe autowave processes in a catalytic fixed bed, which takes into account changes in coefficients of interphase heat and mass transfer and thermal conductivity of the catalytic bed, depending on the current values of system parameters. The behavior of the phase trajectories of the dynamic system is studied by methods of qualitative and numerical analysis, and an effective technique is proposed for searching for a phase trajectory corresponding to the autowave solution of the problem. Numerical studies of the mathematical model of autowave processes are performed, and the effect of system parameters on technological characteristics of the process, such as the maximum temperature and wave-propagation velocity, is considered.
APPLICATION OF CATALYTIC COMBUSTION CHAMBERS OF DECENTRALIZED CONTROL
V.N. Parmon, Z.R. Ismagilov, O.N. Favorskii*, A.A. Belokon*, V.M. Zakharov* (*Baranov Central Institute of Aviation Motors, Moscow, Russia)
Herald Russ. Acad. Sci., 77(9) (2007) pp. 819-826.
The objective of the paper is comprehensive analysis of catalytic combustion chambers for present-day gasturbine units carried out at the BIC SB RAS and Baranov Central Institute of Aviation Motors. The results demonstrate the possibility of development of efficient combustion chambers using domestic high technologies.
CATALYTIC SO2 REDUCTION FOR PURIFICATION OF WASTE GASES OF NONFERROUS-METALS INDUSTRY. TECHNOLOGIES AND CATALYSTS
Z.R. Ismagilov, S.R. Khairulin, S.A. Yashnik, I.V. Ilyukhin* (*JSC MMC Norilsk Nickel, Norilsk, Russia)
Herald of al-Farabi Kazakh National University, ser. Chem., 3(47) (2007) pp. 45-63.
The paper reviews the technologies for purification of waste gases of nonferrous-metals industry. Detailed description of catalytic technologies of SO2 reduction to elemental sulfur is given. Catalytic systems for SO2 reduction and methods of its preparation are reviewed
IMPROVEMENT AND DEVELOPMENT OF CATALYTIC PROCESSING OF WASTE GASES IN VANYUKOV AND FLASH SMELTING FURNACES
Z.R. Ismagilov, S.R. Khairulin, S.A. Yashnik, V.N. Parmon, I.V. Ilyukhin* (*JSC MMC Norilsk Nickel, Norilsk, Russia)
Non-Ferrous Met., 7 (2007) pp. 80-85.
Presented are the results of laboratory and pilot tests of the processes of catalytic SO2 reduction to elemental sulfur with methane and syn-gas. It is concluded that low-temperature process of SO2 catalytic reduction with syn-gas has advantages over homogeneous and catalytic processes of sulfur dioxide reduction with methane.
ACTIVITY OF NEW DOMESTIC ALUMINA CATALYST OF CLAUS PROCESS
O.I. Platonov*, A.G. Ryabko*, L.Sh. Tsemekhman*, P.N. Kalinkin, O.N. Kovalenko, A.Yu. Roslyi* (*JSC “Gipronikel' Institute”, St. Petersburg, Russia)
Catal. Ind., 2 (2007) pp. 54-59.
Results of industrial tests (from 02.04.2003 to 26.06.2006) of new domestic alumina catalyst, AO-NKZ-2 (AO-MK-2), +6,6 mm fraction, in Claus reactor of coke gas purification line of Magnitogorsk metallurgical plant at 245−260°C and 2000 h−1 are generalized. It has been found that the activity of AO-NKZ-2 catalyst in Claus reaction matches that of best foreign analogs (DR «Rhone-Poulenc» and CR-31 «La Roche Chemicals»). Yearly irreversible aging rate of AO-NKZ-2 in hydrogen sulphide conversion does not exceed 2−3 %, which provides at least 7−10 year catalyst operation lifetime in Claus reactors. To increase the economical efficacy of Claus equipment, it is recommended to use specialized catalysts during the hydrolysis of organosulphur compounds and low-temperature Claus conversion steps.
REAL-TIME CONTROL OF SOLID-PROPELLANT COMBUSTION BY A CATALYTIC METHOD
N.N. Kundo, V.V. Romankov, V.I. Simagina, I.V. Eroshkina
Combust., Explosion, Shock Waves, 43(1) (2007) pp. 73-77.
Principles of contact catalysis of combustion are described. The essence of this process implies that a block catalyst contacting the surface of the burning propellant specimen increases the burning rate and allows controlling combustion at a temperature of 400 to 600°C with formation of a large volume of versatile gaseous products, i.e., is the basis for creating lowtemperatures gas generators.
THE THERMODYNAMIC CHARACTERISTICS OF FORMATION OF NANOPARTICLES FROM SUPERCRITICAL SOLVENTS
V.I. Anikeev, A. Yermakova
Russ. J. Phys. Chem. A, 81(12)(2007) pp. 2024-2029.
A thermodynamic model for calculating equilibria and the phase states of fluid-solid systems over wide temperature, pressure, and composition ranges was suggested. Calculations were performed to determine the parameter regions where a substance was isolated in the form of a solid depending on the chemical composition of the initial mixture and the amounts of and ratio between the solvent and antisolvent in it. The calculations were performed for a model system containing ethanol, carbon dioxide, and phenanthrene. The rapid expansion of this supercritical fluid was simulated to model the conditions of the formation of a solid (phenanthrene) and nanoparticles based on it. It was shown that the selection of the state parameters of the supercritical mixture determined the optimum conditions of solid state formation as the fluid expanded.
THE THERMAL ISOMERIZATION OF TERPENE COMPOUNDS IN SUPERCRITICAL ALCOHOLS
V.I. Anikeev, A. Yermakova, A.M. Chibiryaev*, I.V. Kozhevnikov*, P.E. Mikenin* (*Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. J. Phys. Chem. A, 81(5)(2007) pp. 711-716.
The experimental data obtained were used to construct a kinetic model of the isomerization of α-pinene in supercritical ethanol. The model took into account the influence of both temperature and pressure on the rate and selectivity of the reaction.
THERMAL ISOMERIZATION OF α-PINENE IN SUPERCRITICAL ETHANOL
A. Yermakova, A.M. Chibiryaev*, I.V. Kozhevnikov*, P.E. Mikenin*, V.I. Anikeev (*N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Chem. Eng. Sci., 62(9) (2007) pp. 2414-2421.
The experimental study followed by mathematical processing of the data showed that supercritical ethanol is an effective reaction medium for thermal isomerization of α-pinene. Rate of the reaction in supercritical solvent is by several orders of magnitude greater than the rate observed under normal conditions, with selectivity to the target reaction products being retained. The study allowed for the first time to obtain the kinetic model of -pinene isomerization in supercritical ethanol that takes into account temperature and pressure effect on the reaction rate and selectivity.
COMPARATIVE THERMOLYSIS OF β-AND α-PINENES IN SUPERCRITICAL ETHANOL: THE REACTION CHARACTERIZATION AND ENANTIOMERIC RATIOS OF PRODUCTS
A.M. Chibiryaev*, A. Yermakova, I.V. Kozhevnikov*, O.I. Sal’nikova**, V.I. Anikeev (*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Russ. Chem. Bull., 56(6) (2007) pp. 1234-1238.
The thermolysis of β-pinene and the cothermolysis of an equimolar mixture of β-and α-pinenes in supercritical ethanol were carried out. The reaction of β-pinene affords β-myrcene as the major product (>70%). Considerable differences in the temperature dependence of the reaction rate were revealed for the transformations of β-pinene into β-myrcene and of α-pinene into limonene. The preexponential factors and the activation energies were calculated. The enantiomeric ratios of the thermolysis products of β-and α-pinenes and limonene were estimated. The starting monoterpenes do not undergo racemization during thermolysis. The thermolysis of enantiomerically pure α-pinene affords racemic (±)-limonene, whereas (−)-β-pinene gives (−)-limonene. The enantiomeric ratio in the latter remains equal to the enantiomeric purity of the starting β-pinene.
COMBUSTION CHARACTERIZATION OF HYDRAZINIUM NITRATE/ENERGETIC BINDER/ALEX BASED MODEL PROPELLANTS
V.E. Zarko*, V.N. Simonenko*, G.I. Anisiforov, A.V. Aparin (*Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia)
Aerospace Sci. Technol., 11(1) (2007) pp. 13-17.
The hydrazinium nitrate (N2H4*HNO3-HN) can be considered as a candidate for using instead of ammonium perchlorate (AP) in eco-friendly solid propellant formulations. In combination with energetic binder it provides reasonably high energetic parameters of solid propellant. In addition, the substitution of AP by HN leads to decrease in the combustion temperature. The combustion of the HN based metallized propellants containing energetic binder has been investigated. The effect of partial substitution of commercial Al powder by Alex on the propellant combustion characteristics has been examined. The burning law was measured in the pressure range 20-80 atm, the ignition delay time and temperature profile were measured at atmospheric pressure. Some qualitative observations on the combustion behavior of the propellants under study have been made by analyzing the video camera and recoil force transducer records.
ON ONE APPROACH TO THE W-METHODS CONSTRUCTION FOR STIFF ODE SYSTEMS
V.A. Vshivkov*, O.P. Stoyanovskaya (*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia)
Comput. Technol., 12(4) (2007) pp. 42-58.
A new approach for construction of W-methods for stiff system of ODE is presented. Using the proposed idea, a W-modification of the onestage Rozenbrok scheme has been developed. Some computational features of the proposed new method are described.
APPLICATION OF THE CHEMPAK PACKAGE FOR MODELING OF GAS-DYNAMICS REACTOR
V.A. Vshivkov*, G.G. Chernykh*, O.P. Stoyanovskaya, A.V. Snytnikov* (*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia)
Comput. Technol., 11(1) (2006) pp. 35-51.
The ChemPAK program package for solving the direct problems of chemical kinetics with arbitrary number of chemical reactions is suggested. The package contains an expandable library of computational modules and provides a function of data transfer to multiprocessor. The process of C1-C2 hydrocarbon's pyrolysis in gas-dynamics reactor with emission has been numerically simulated using the ChemPak software package.
THE PARALLEL ALGORITHM AND PROGRAM KEY7D FOR SOLUTION OF NON-STATIONARY 3D PROBLEMS OF GRAVITATIONAL PHYSICS
E.A. Kuksheva, V.N. Snytnikov
Comput. Technol., 12(1) (2007) pp. 35-44.
An effective parallel Key7D code for solution of 3D problems of collisionless gravitational physics in Cartesian coordinates is developed. The discrete analogue of fundamental solution of Poisson's Equation is used to determine boundary conditions during calculation of the gravitational potential. For this procedure an efficient parallel algorithm is developed. A quasistationary solution of the system is p resented using the Key7D program.
STRATEGIES FOR DEVELOPMENT OF A PARALLEL PROGRAM FOR PROTOPLANETARY DISC SIMULATION
S.E. Kireev*, E.A. Kuksheva, A.V. Snytnikov*, N.V. Snytnikov*, V.N. Snytnikov, V.A. Vshivkov* (*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia)
Lect. Notes Comp. Sci., “Parallel Comp. Technol.”, 4671 (2007) pp. 128-139.
Protoplanetary disc simulation must be done first, with high precision, and second, with high speed. Some strategies to reach these goals are presented in the paper. They include: the reduction of the 3D protoplanetary disc model to quasi-3D, the use of fundamental Poisson equation solution, the simulation in the natural (cylindrical) coordinate system and computation domain decomposition. The domain decomposition strategy is shown to reach the simulation goals the best.
PRODUCTION OF NANOMATERIALS BY VAPORIZING CERAMIC TARGETS IRRADIATED BY A MODERATE-POWER CONTINUOUS-WAVE CO2 LASER
V.N. Snytnikov, D.A. Dubov, Vl.N. Snytnikov, V.I. Zaikovskii, A.S. Ivanova, V.O. Stoyanovskii, V.N. Parmon
J. Appl. Mech. Techn. Phys., 48(2) (2007) pp. 292-302.
The efficiency of utilization of CO2 laser energy for vaporization of Al2O3 ceramics is evaluated using a mathematical model for the interaction of laser radiation with materials. It is shown that the calculated efficiency of radiation-energy utilization is not higher than 15% at a radiation power density of 105 W/cm 2 on the target. On the experimental facility designed for the synthesis of nanopowders, a vaporization rate of 1 g/h was achieved for Al2O3, which corresponds to a 3% efficiency of radiation-energy utilization. The dependence of the characteristic particle size of a zirconium oxide nanopowder on helium pressure in the range of 0.01–1.00 atm was studied. Results of experiments on vaporization of multicomponent materials (LaNiO3 and the Tsarev meteorite) are given.
STUDY OF 3D DYNAMICS OF GRAVITATING SYSTEMS USING SUPERCOMPUTERS: METHODS AND APPLICATION
N.V. Snytnikov*, V.A. Vshivkov*, V.N. Snytnikov (*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia)
Lect. Notes Comp. Sci., “Parallel Comp. Technol.”, 4671 (2007) pp. 162-173.
Parallel numerical code for solving problems of stellar dynamics is described. The code is based on numerical solving of Poisson and Vlasov equations in cylindrical coordinates using particle-in-cells method. The code is designed for use on supercomputers with distributed memory. It is considered different possible strategies of parallelization according to initial technical parameters of numerical methods and physical conditions of the model. The results of numerical simulations for the following problems of stellar dynamics: investigation of influence of central potential on the vertical motions of thin gravitating disk; stability of uniform sphere with anisotropic distribution of velocity; numerical approximation of equilibrium states of gravitating systems are presented.
AN ALGORITHM FOR THE THREE-DIMENSIONAL MODELING OF ULTRARELATIVISTIC BEAMS
M.A. Boronina, V.A. Vshivkov*, E.B. Levichev**, S.A. Nikitin**, V.N. Snytnikov (*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia; **Budker Institute of Nuclear Physics, Novosibirsk, Russia)
Numer. Meth. Progr., 8 (2007) pp. 352-359.
An algorithm for modeling the interaction charged particle beam effects in the three-dimensional ultrarelativistic case is considered. An algorithm to compute initial and boundary conditions when introducing an artificial potential is proposed. Some numerical test results for prescribing boundary conditions and for solving the problem of beam focusing at the region center are discussed.
REFORMING OF DIMETHYL ETHER TO HYDROGEN-RICH GAS FOR HT PEM FUEL CELLS
V.A. Sobyanin, V.A. Kirillov, S.D. Badmaev, V.D. Belyaev, V.D. Mescheryakov
Chem Eng. Trans., 11 (2007) pp. 929-934.
Experimental results on the performance of the catalysts for DME steam reforming (DME SR) to hydrogen-rich gas and on HT PEMFC operation with pure hydrogen and reformate gas have been analyzed. Electric efficiency of the DME fuelled HT PEM FC system has been estimated. It has been found that expected electric efficiency of the system equals 38–41.5% (LHV).
CATALYTIC REFORMERS WITH MEMBRANE SEPARATION OF HYDROGEN
B.N. Lukyanov
Chem. Sustain. Devel., 15(6) (2007) pp. 625-641.
Catalytic processes for hydrogen generation based on water-permeable membranes are described. Various types of solid membranes for hydrogen extraction from gas mixtures are considered. Design of catalytic membrane-integrated reformers is discussed to demonstrate their advantages against traditional fuel cell reactors. Relevant mathematical models are described and some modeling results on the reactors with membrane isolation of hydrogen are presented. Some prospects of employing these catalytic reactors for hydrogen energetics and for motor vehicles are analyzed.
A MULTICAPILLARY GAS CHROMATOGRAPHIC COLUMN WITH A SOL-GEL SORBENT BASED ON ALUMINUM OXIDE
Yu.V. Patrushev, Yu.G. Vervekin, V.I. Sidelnikov
Russ. J. Phys. Chem. A, 81(3) (2007) pp. 488-491.
A multicapillary gas chromatographic column with an adsorption layer based on alumina was prepared. The column allowed the high-speed separation of C1-C4 light hydrocarbons to be performed in 8÷12 s. The possibility of creating columns with various selectivities was demonstrated.