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).
Bahrein |
1 |
India |
2 |
South Korea |
1 |
Belarus |
2 |
Ireland |
1 |
Spain |
9 |
Belgium |
5 |
Israel |
6 |
Singapore |
4 |
China |
16 |
Italy |
8 |
Switzerland |
4 |
Czechia |
4 |
Japan |
8 |
Thailand |
1 |
Egypt |
1 |
Montenegro |
4 |
Turkey |
2 |
Finland |
2 |
Netherlands |
15 |
Ukraine |
3 |
France |
10 |
Poland |
6 |
United Kingdom |
8 |
Germany |
28 |
Saudi Arabia |
4 |
USA |
6 |
Greece |
32 |
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|
|
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Canada |
1 |
Germany |
17 |
South Korea |
7 |
China |
9 |
Italy |
4 |
Spain |
1 |
DPRK |
5 |
Japan |
10 |
Turkey |
1 |
Estonia |
1 |
Netherlands |
3 |
USA |
13 |
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:
Coordinators: Prof. O. Lapina (BIC), Prof. J.-F. Bodart (Université des Sciences et Technologies de Lille), Prof. Jean-Baptiste d’Espinose de la Caillerie (Ecole Supéireure de Physique et de Chimie Industrielles).
INDIA
In the frame of Indo-Russian Integrated Long Term Programme of cooperation in science
and technology (ILTP) BIC collaborates with:
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
YUGOSLAVIA
The cooperation in the frame of the agreement between RAS and Serbian Academy of Sciences and Arts on the Project “Novel Catalytic Materials and Technologies”. Coordinators: Acad. V. Parmon (BIC), Acad. P. Putanov, Prof. B. Anadzievic (Serbian Academy of Sciences and Arts).
CZECH REPUBLIC
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). 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).
C-O BOND SCISSION IN METHOXIDE ON Pd NANOPARTICLES: A DENSITY FUNCTIONAL STUDY
I.V. Yudanov, K.M. Neyman*, N. Rösch**
(*Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain; **Technische Universität München, Garching, Germany)
Phys. Chem. Chem. Phys., 8 (2006) pp. 2396-2401.
C-O bond scission of methoxide species adsorbed at the surface of Pd nanoparticle was studied by DF calculations for the example of cuboctahedral Pd79. To investigate different locations of adsorbed intermediates as well as the transition state of C-O bond scission, a substrate model was used, which allows one to consider adsorbates without any local geometry restrictions. In contrast to reaction sites on the flat Pd(111) surface and on extended facets, scission of the C-O bond of methoxide at cluster edges is exothermic by ~40 kJ/mol and the decomposition product CH3 is found to be stabilized there. However, the high calculated activation barrier, ~140 kJ/mol, implies only a very slow reaction compared to dehydrogenation of CH3O.
ADSORPTION OF Cu4, Ag4 AND Au4 PARTICLES ON THE REGULAR MgO(0 0 1) SURFACE: A DENSITY FUNCTIONAL STUDY USING EMBEDDED CLUSTER MODELS
Ch. Inntam*, L.V. Moskaleva*, I.V. Yudanov, K.M. Neyman**,***, N. Rösch*
(*Technische Universität München, Garching, Germany; **Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain; ***Universitat de Barcelona, Barcelona, Spain)
Chem. Phys. Lett., 417(4-6) (2006) pp. 515-520.
Cu4, Ag4, and Au4 species adsorbed on the regular MgO(0 0 1) surface are studied using a density functional method and cluster models embedded in an elastic polarizable environment. The structure of the coinage metal tetramers is only slightly distorted by adsorption on the oxide surface compared to the rhombic-planar arrangement in the gas phase. The most stable adsorption complexes of all three systems feature upright metal planar particles with the M4 moiety orthogonal to the surface and two metal atoms attached to surface oxygen anions. Au4 and Cu4 exhibit substantially stronger binding to the surface than Ag4.
A DFT STUDY OF HYDROGEN–DEUTERIUM EXCHANGE OVER OXIDIZED AND REDUCED GALLIUM SPECIES IN Ga/HZSM-5 ZEOLITE
I.V. Kuzmin*, G.M. Zhidomirov, E.J.M. Hensen**
(*Zelinsky Institute of Organic Chemistry, Moscow, Russia; **Schuit Institute of Catalysis, Eindhoven University of Technology, Eindhoven , The Netherlands)
Catal. Lett., 108(3–4) (2006) pp. 187-191. Quantum-chemical calculations give insight in the experimentally observed higher rate of hydrogen– deuterium exchange for oxidized Ga/HZSM-5 over reduced Ga/HZSM-5. The reaction is computed to be more facile over reduced (Ga+) than over oxidized (GaO+) cations. The difference lies in the difficult formation of active GaH2+ cations from Ga+ compared to facile hydrogen dissociation over GaO+ to give active GaHOH+ cations. Neutral gallium oxide clusters are shown to have a lower intrinsic activity than GaO+ cations.
INTERACTION OF Co6 CLUSTER WITH γ-ALUMINA SURFACE: A QUANTUM CHEMICAL STUDY
M.N. Mikhailov*, G.M. Zhidomirov, A.Yu. Krylova*
(*Zelinsky Institute of Organic Chemistry, Moscow, Russia)
Russ. Chem. Bull., 10 (2005) pp. 2264-2269. The interaction of Co6 cluster with partially dehydroxylated γ-alumina surface was studied by the DFT method. Hydrogen atoms of surface hydroxyl groups can be transferred to the metal particle to form partially oxidized cobalt states. The energy characteristics of hydrogen transfer were determined and changes in the electronic structure of supported Co6 particles were characterized.
MoS2 SINGLE SLAB AS A MODEL FOR ACTIVE COMPONENT OF HYDRODESULFURIZATION CATALYST: A QUANTUM CHEMICAL STUDY. 1. MOLECULAR AND ELECTRONIC STRUCTURE OF Mo12S24 MACROMOLECULE AND ITS ADSORPTION COMPLEX WITH H2S
I.I. Zakharov, A.N. Startsev
Russ. Chem. Bull., 10 (2005) pp. 2259-2263.
The molecular and electronic structure of Mo12S24 macromolecule as the MoS2 single slab structure was calculated by the density functional theory (DFT) method with the B3P86 hybrid exchange-correlation functional. The results of calculations point to slight relaxation of coordinatively unsaturated Mo and S atoms, which is consistent with the published data. The calculated width of the forbidden band (0.85-0.98 eV) is comparable with the experimental value (1.30 eV) and similar to that obtained from DFT calculations with periodic boundary conditions (0.89 eV). The surface Mo centers in the Mo12S24 macromolecule are more reduced than the internal Mo(IV) atoms. In order to characterize the adsorption capacity of coordinatively unsaturated Mo centers, a Mo12S24•6H2S adsorption complex was calculated. The structure and energy characteristics of the adsorption complex point to a weak donor-acceptor interaction of the π-lone pair of H2S molecule with the surface (reduced) Mo centers. The active center of thiophene hydrodesulfurization catalysts is formed as a result of the oxidative addition of hydrogen followed by occlusion of hydrogen into the MoS2 matrix.
THE MOLECULAR AND ELECTRONIC STRUCTURE OF THE Mo12S24 MACROMOLECULE AS A MODEL OF THE ACTIVE COMPONENT OF A HYDRODESULFURIZATION CATALYST
I.I. Zakharov, O.V. Voroshina, A.N. Startsev
Russ. J. Phys. Chem., 80(7) (2006) pp. 1083-1087.
The density functional theory (DFT) with the B3P86 hybrid exchange-correlation functional was used to calculate the molecular and electronic structure of the Mo12S24 macromolecule as a single MoS2 layered structure slab. Calculations with geometry optimization are indicative of insignificant relaxation of the coordinatively unsaturated Mo and S atoms, which corresponds with the literature DFT data on the MoS2 single slab obtained with periodic boundary conditions. The calculated forbidden band width (0.85–0.98 eV) is comparable with its experimental value (1.30 eV) and the results of DFT calculations of MoS2 with periodic boundary conditions (0.89 eV). An analysis of the electronic state of the surface Mo centers in the Mo12S24 macromolecule showed that these centers were reduced to a greater degree than the Mo(IV) atoms in the bulk. The adsorption complex between the Mo12S24 macromolecule and six H2S molecules was calculated to characterize the adsorption ability of the coordinatively unsaturated Mo centers. The structure and energy characteristics of the adsorption complex corresponded to weak donor-acceptor interaction between the -lone pair of H2S and the surface (reduced) Mo centers. The suggestion was made that the active center of the catalytic cycle of thiophene hydrodesulfurization should induce the oxidative addition of H2 followed by the occlusion of hydrogen into the MoS2 matrix.
QUANTUM-CHEMICAL ANALYSIS OF THE CuCl2 MOLECULE
S.F. Ruzankin, V.F. Anufrienko, S.A. Yashnik, Z.R. Ismagilov
J. Struct. Chem., 47(3) (2006) pp. 404-412.
This paper reports on quantum-chemical analysis of the linear structure of CuCl2 by Hartree-Fock (HF) and density functional theory (DFT) methods and also by time-dependent HF (TD HF) and DFT (TD DFT) techniques. Using pure DFT exchange correlation functional (B3LYP) yields the best agreement with the experimental electronic spectra of CuCl2. In this case, the odd electron is delocalized over the molecule, spin density on copper being 0.27. The ground state of the CuCl2 molecule is 2Πg with linear geometry.
ASFMS: A PROGRAM PACKAGE FOR AB INITIO CALCULATION OF ABSORPTION SPECTRA BY FULL MULTIPLE SCATTERING
S.Ph. Ruzankin
Comp. Mater. Sci., 36(1-2) (2006) pp. 184-188.
The program package ASFMS for ab initio self- consistent field (SCF) all-electron full multiple scattering (MS) computations of electron structure and absorption spectra of large systems was developed. ASFMS can compute the X-ray absorption fine structure (XAFS) and near-edge structure (XANES) spectra. Unlike other programs ASFMS can be applied to calculations of pre-edge structure and transition intensity in ultraviolet region. Another advantage of ASFMS consists in using additional cluster boundary conditions for modeling of ionic and covalent solids. Effective algorithms are implemented to reduce the time of the computation and storage.
NATURE OF THE CHEMICAL BOND OF HYDROGEN AND OXYGEN ATOMS WITH Pt(100) SURFACE: QUANTUM CHEMICAL CALCULATION AND DISAPPEARANCE POTENTIAL SPECTRA
V.M. Tapilin, V.D. Tsybiktarov, A.R. Cholach
Russ. J. Struct. Chem., 47(5) (2006) pp. 808-812.
Electronic structures of clean, hydrogen covered, and oxygen covered Pt(100)-(1x1) surface have been calculated. Both absorbates form surface subzones localized below the metal conduction band and overlapping partially with it. Furthermore, the local density of states (LDOS) reveals the peaks of the resonant state on the absorbed atoms which are narrower for hydrogen than for oxygen. The comparison of LDOS on absorbed and Pt atoms shows that subzone surface states are responsible for the covalent component of the chemical bond between absorbed and platinum atoms, while resonant states make the ionic contribution. The obtained LDOS were used to calculate disappearance potential spectra. Theoretical spectra are well consistent with experimental ones.
ELECTRONIC STRUCTURE OF ZrO2 AND HfO2
T.E. Perevalov*, A.V. Shaposhnikov*, K.A. Nasyrov*, D.V. Gritsenko*, V.A. Gritsenko*, V.M. Tapilin
(*Institute of Semiconductor Physics, Novosibirsk, Russia)
In “Defects in High-k Gate Dielectric Stacks: Nano-Electronic Semiconductor Devices”, NATO Science Series II: Mathematics, Physics and Chemistry, Ed. E. Gusev, Springer, 2006, pp. 423-434.
Band structures, density of states and effective masses of electrons and holes of cubic, tetragonal and monoclinic phases of ZrO2 and HfO2 have been calculated. Oxygen vacancy has been modeled by removing off one oxygen atom from 12-atom monoclinic cell. Incorporation of oxygen vacancy leads to formation of new filled subband formed mostly by d-electrons of the metals. Enormously high leakage current, observed in ZrO2 and HfO2 is explained by multi-phonon trap ionization model.
TIME SAVING TECHNIQUES FOR ELECTRONIC STRUCTURE CALCULATIONS OF INFINITE AND SEMI-INFINITE CRYSTALS, INTERFACES, AND SLABS OF ARBITRARY THICKNESS
V.M. Tapilin
Comp. Mater. Sci., 36(1-2) (2006) pp. 106-111. Hard confined functions (HCF) are proposed as a basis set for electronic structure calculations. The basis functions have enough number of continuous derivatives to perform space integrations numerically with desired accuracy. Replacing unconfined basis functions in ADF-AND package by HCF with cut-off radiuses of the order of the nearest neighbor distance leads to the reduction of the time of computations without loosing the accuracy. For the crystals with surfaces, special techniques based on representation of the wave function as a linear combination of a finite number of HCF and Bloch waves, were elaborated. Exact finite sets of equations for coefficients of HCF and Bloch waves have been developed. The order of the sets depends only on the thickness of a perturbed region, but not on the size of the whole system. For integration of the density of states over perpendicular to the surface wave vector component and energy the residue theorem and a shift of the energy path into the complex plane are used.
THE VARIATIONS OF g-TENSOR PRINCIPAL VALUES IN REDUCED [2Fe-2S] CLUSTER OF IRON-SULFUR PROTEINS
A.A. Shubin, S.A. Dikanov*
(*Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia)
Appl. Magn. Reson., 30(3-4) (2006) pp. 399-416.
This article discusses the present status of the theoretical and experimental studies of the electronic structure of the reduced [2Fe-2S] cluster with special emphasis on the g-tensor variations in the Rieske-type proteins. The necessity of this analysis is dictated by the fact that the changes in the EPR lineshape of the reduced cluster are broadly exploited as the basis for different mechanistic conclusions in the structure- function studies of the bc1/b6f families.
ANALYSIS OF THE STRUCTURAL SPECIFICITY OF ZrO2 NANOPARTICLES IN PILLARED CLAYS BY MODELING OF THE CONDENSATION PROCESS IN ZrOCl2.8H2O SOLUTIONS
N.V. Mezentseva, V.A. Sadykov, V.I. Avdeev, V.L. Kuznetsov
Mater. Res. Soc. Symp. Proc., 894 (2006) LL06-05.1-05.6.
A combination of quantum-chemical approaches including DFT, semiempirical PM3 and molecular mechanics (force field ММ+) methods has been applied for analysis of the structure of polynuclear hydroxocomplexes of Zr in diluted solutions of its oxochloride as precursors of zirconia nanoparticles in zirconia-pillared clays. Relative stability of complexes differing by their size and shape has been estimated.
SURFACE CHARACTERIZATION OF NANOSTRUCTURED ZIRCONIA CATALYSTS BY ESR SPECTROSCOPY USING O2- RADICAL ANIONS AS SPIN PROBES
N.V Mezentseva, A.F Bedilo, A.M Volodin, V.A. Sadykov
Mater. Res. Soc. Symp. Proc., 900E (2006) O06-11.1-11.6.
O2- radical anions generated by adsorption of hydrogen peroxide or NO + O2 mixture were used as spin probes for EPR characterization of nanostructured zirconia catalysts, including pillared clays. Similarities and significant discrepancies observed in the formation of oxygen radical anions over catalysts with different composition and surface structure by the two methods are discussed..
KOOPMANS' THEOREM IN THE ROHF METHOD: CANONICAL FORM FOR THE HARTREE-FOCK HAMILTONIAN
B.N. Plakhutin, E.V. Gorelik, N.N. Breslavskaya*
(*Kurnakov Institute of General and Inorganic Chemistry, Moscow, Russia)
J. Chem. Phys., 125(21)(2006) pp. 204110 (10 pages)
Since the classic work of Roothaan [Rev. Mod. Phys. 32, 179 (1960)], the one-electron energies of a ROHF method are known as ambiguous quantities having no physical meaning. Together with this, it is often assumed in present-day computational studies that Koopmans' theorem is valid in a ROHF method. In this work the specific dependence of orbital energies on the choice of the basic equations in a ROHF method which are the Euler equations and different forms of the generalized Hartree-Fock equation are analyzed. The authors first prove that the one-electron open-shell energies εm derived by the Euler equations can be related to the respective ionization potentials Im via the modified Koopmans' formula Im=− εm/fm where fm is an occupation number. As compared to this, neither the closed-shell orbital energies nor the virtual ones derived by the Euler equations can be related to the respective ionization potentials and electron affinities via Koopmans' theorem. Based on this analysis, the new (canonical) form for the Hamiltonian of the Hartree-Fock equation is derived, the eigenvalues of which obey Koopmans' theorem for the whole energy spectrum. A discussion of new orbital energies is presented on the examples of a free N atom and an endohedral N@C60 (Ih). The vertical ionization potentials and electron affinities estimated via Koopmans' theorem are compared with the respective observed data and, for completeness, with the respective estimates derived via a ΔSCF method. The agreement between observed data and their estimates via Koopmans' theorem is qualitative and, in general, appears to possess the same accuracy level as in the closed-shell SC.
GRAZERS AND GRASS: MONTE CARLO SIMULATIONS
<./B>V.P. Zhdanov
BioSystems, 85(3) (2006) pp. 219-224. To illustrate the interplay between grazers and grass, a novel Monte Carlo model is presented including grass-island growth, consumption of grass by grazers, and birth, migration and death of grazers. The rates of the former and three latter processes are assumed to depend on the environment so that the conventional mean-field approximation does not hold (in particular, the model takes into account that grass grows on the grass-island boundaries, and grazers are mobile and prefer to stay on the areas covered by grass). Due to the feedback between various processes, as expected, the model predicts stable regimes and irregular oscillations of the area of the grass islands and grazer population. The patterns observed are however different compared to those predicted by conventional Monte Carlo prey–predator models. Specifically, there is no tendency for grazers and grass to segregate. The mean-field version of the model is briefly discussed as well.
TRANSIENT STOCHASTIC BISTABLE KINETICS OF GENE TRANSCRIPTION DURING THE CELLULAR GROWTH
V.P. Zhdanov
Chem. Phys. Lett., 424(4-6) (2006) pp. 394-398. The feedback between mRNA and regulatory-protein production may result in bistability of gene transcription. If the mRNA and/or protein number are low, one can observe transcriptional ‘bursts’ in this case provided that the intracellular conditions are steady. Monte Carlo simulations show that for biologically reasonable kinetic parameters this effect may easily disappear if the transcription occurs during the cellular growth and division.
SUPPRESSION OF BINDING EVENTS VIA EXTERNAL PERTURBATION WITH EMPHASIS ON QCM
V.P. Zhdanov, M. Edvardsson*, F. Hook**, B. Kasemo*
(*Chalmers University of Technology, Göteborg, Sweden; **Lund University, Lund, Sweden)
Chem. Phys. Lett., 424(1-3) (2006) pp. 214-217. Recent experiments indicate that the external perturbations, related e.g. to high-amplitude shear oscillations of the surface of a quartz crystal microbalance sensor, may suppress binding of mesoscopic aggregates (e.g., polystyrene spheres, vesicles, large proteins, etc.) to the surface. Using a simple kinetic model, equations were derived making it possible to conceptually understand and to mathematically describe what may happen in such experiments.
SIGNALING BETWEEN CELLS ATTACHED TO A SURFACE
V.P. Zhdanov, B. Kasemo*
(*Chalmers University of Technology, Göteborg, Sweden)
Phys. Rev. E,74 (2006) 021915 (6 pp.).
A kinetic model allowing one to classify likely scenarios of protein-mediated communication between attached cells of two distinct types is presented. Upontreatment, messenger proteins, synthesized in type-1 cells, are considered to penetrate the external membrane of these cells, diffuse in the extracellular medium, associate with the receptors in the external membrane of cells of both types, and induce intracellular signal transduction cascades, influencing the development of cells. Protein degradation inside and outside cells is taken into account as well.
IMAGING AND MANIPULATION OF ADSORBED LIPID VESICLES BY AN AFM TIP: EXPERIMENT AND MONTE CARLO SIMULATIONS
K. Dimitrievski**, A. Zach**, V.P. Zhdanov, B. Kasemo**
(*Göteborg University, Göteborg, Sweden; **Chalmers University of Technology, Göteborg, Sweden)
Colloids Surf. B: Biointerf., 47(2) (2006) pp. 115-125.
Single lipid vesicles adsorbed on SiO2 were manipulated using an atomic force microscope (AFM) operated in contact mode. For large force setpoints, single vesicles were either pushed sideways or ruptured by the tip, depending on the tip type (sharp or blunt) used, while for small force setpoints the vesicles were imaged by the tip. To extend the interpretation of and to guide the experiment, it has been developed a generic model of the vesicle–tip– substrate system and performed Monte Carlo simulations, addressing the influence of force setpoint and tip speed and shape on the type of imaging or manipulation observed. Specifically, it has been explored AFM-image height and width variations versus force setpoint, typical AFM images for small and large force setpoints, tip-induced vesicle strain versus force setpoint, typical vesicle shapes during pushing for different tip speeds, and the details of vesicle rupture induced by the tip.
ADSORPTION AND SPONTANEOUS RUPTURE OF VESICLES COMPOSED OF TWO TYPES OF LIPIDS
V.P. Zhdanov, K. Dimitrievski*, B. Kasemo*
(*Chalmers University of Technology, Göteborg, Sweden)
Langmuir, 22(8) (2006) pp. 3477-3480.
To analyze the adsorption of single vesicles composed of two types of lipids (e.g., zwitterionic and positively charged lipids or zwitterionic and negatively charged lipids), a statistical model is proposed taking into account lipid-surface interactions, lipid-lipid lateral interactions, and vesicle bending energy. Treatment specifies how these parameters govern vesicle adsorption, shows how the radius of the vesicle-surface contact area may depend on the vesicle composition, and clarifies the conditions for vesicle rupture.
SIMULATION OF THE CHARGE AND POTENTIAL DISTRIBUTION IN THE DOUBLE LAYER FORMED BY POLYMER ELECTROLYTE
V.P. Zhdanov, B. Kasemo*
(*Chalmers University of Technology, Göteborg, Sweden)
Electrochem. Comm., 8(4) (2006) pp. 561-564.
Monte Carlo simulations of phase separation on the nm scale in the double layer formed by wetted NAFION or NAFION-type polymer electrolyte near the charged metal surface is presented. The results obtained indicate that the phase separation may cause appreciable spatial fluctuations of the potential near the surface. If e.g. the drop of the potential in the double layer is about 1 V, the amplitude of the fluctuations of the potential may be 0.2–0.3 V. Such fluctuations may influence the rate of electrochemical reactions.
KINETICS OF ELECTROCHEMICAL O2 REDUCTION ON Pt
V.P. Zhdanov, B. Kasemo*
(*Chalmers University of Technology, Göteborg, Sweden)
Electrochem. Comm., 8(7) (2006) pp. 1132-1136
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. Recent DFT calculations indicate that during this reaction the atomic-oxygen coverage may be appreciable. To adjust these two findings, the reaction kinetics corresponding to the dissociative and associative mechanisms with participation of atomic oxygen was analyzed. If the reaction steps are described by using the Langmuir equations, the kinetics is predicted to be first order only in the situations when the O coverage is low. With O–O lateral interactions, the model based on the associative mechanism is able to predict the first-order kinetics in a wide range of pressure even if the O coverage is appreciable.
PROPAGATION OF A REACTION FRONT ACCOMPANIED BY ISLAND FORMATION: CO/Au/Ni(111)
V.P. Zhdanov, R.T. Vang, J. Knudsen, E.K. Vestergaard, F. Besenbacher
(*University of Aarhus, Aarhus C, Denmark)
Surf. Sci., 600(19) (2006) L260-L264.
Recent high-pressure scanning tunneling microscopy studies, performed at room temperature, have explicitly demonstrated the specifics of the CO-mediated removal of Ni atoms from the topmost layer of an Au/Ni(1 1 1) surface alloy. After an incubation period, the reaction is found to start at step edges. On each edge, a large fraction of Ni atoms is removed from the terrace in certain areas, whereas other areas are nearly intact after a given time. With increasing time, the former areas begin to overlap and the reaction front becomes somewhat more homogeneous. The Au atoms remaining behind the front form nm-sized islands. Here, Monte Carlo simulations reproducing all these observations are presented.
RELAXATION OF PLASMONS IN nm-SIZED METAL PARTICLES LOCATED ON OR EMBEDDED IN AN AMORPHOUS SEMICONDUCTOR
V.P. Zhdanov, C. Hägglund*, B. Kasemo*
(*Chalmers University of Technology, Göteborg, Sweden)
Surf. Sci., 599(1-3) (2005) L372-L375.
Relaxation of plasmons, generated optically in nm-sized metal particles, occurs usually via excitation of electron–hole pairs inside the particles. If a metal particle is located on the surface of or embedded in a semiconductor, plasmons may also relax via local field enhanced excitation of electron–hole pairs in the semiconductor. Equations were derived describing the latter relaxation channel in the case when the semiconductor is amorphous or nanocrystalline and show that the ratio of the rates of the two channels may vary in a wide range. In particular, the latter channel may dominate under certain conditions. As an example, the Ag/TiO2 system is briefly discussed
CHARGE DISTRIBUTION ON AND NEAR SCHOTTKY NANOCONTACTS
C. Hagglund*, V.P. Zhdanov
(*Chalmers University of Technology, Göteborg, Sweden)
Physica E, 33(1) (2006) pp. 296-302.
Schottky nanocontacts are formed when nm-sized metal particles are located on the planar surface of a doped semiconductor. The charge distribution on and near such nanocontacts is analyzed in the case of disc-shaped particles. The results of calculations are presented as a function of particle size, semiconductor permittivity, dopant concentration, and Fermi level difference. In contrast to macroscopic junctions, the charging of the metal particle is demonstrated to be proportional to the Fermi level difference and accordingly to the potential difference between the metal and semiconductor, so that the junction exhibits a constant capacitance. The charging of the metal-vacuum metal surfaces may be appreciable, especially for relatively low values of the semiconductor permittivity. The tunneling barrier width at half height is shown to be close to, or less than, 3/8 of the disc diameter.
SELF-SUSTAINED KINETIC OSCILLATIONS IN CO OXIDATION OVER SILICA-SUPPORTED Pt
P.A. Carlsson*, V.P. Zhdanov, M. Skoglundh*
(*Chalmers University of Technology, Göteborg, Sweden)
Phys. Chem. Chem. Phys., 8(23) (2006) pp. 2703-2706.
Isothermal self-sustained kinetic oscillations in CO oxidation over silica-supported Pt at near- atmospheric pressure were studied by combined in situ Fourier transform infrared spectroscopy and mass spectrometry. The use of a specially designed reactor and careful choice of the physical properties of the catalyst and reaction conditions made it possible to eliminate diffusion limitations, to determine the maximum CO oxidation rate per Pt site in the purely kinetic regime and to clarify the mechanism of the oscillations. Specifically, the results obtained indicate that during the high reactive periods the reaction mainly occurs on the oxide surface.
NONADIABATIC RATE PROCESSES ON METAL SURFACE: LIMITATION BY SPIN CONVERSION
V.P. Zhdanov
J. Exp. Theor. Phys., 102(5) (2006) pp. 737-740.
Rate processes occurring on a metal surface may sometimes be limited by spin conversion. A generic model is presented describing this case. The results obtained are compared with the conventional two-state Landau-Zener model and with a multistate model implying one-electron transfer between the reactant and the metal. In this context, the specifics of the dissociative adsorption of O2 on Ag(111) are briefly discussed.
STATISTICAL LATTICE MODEL FOR THE BIMOLECULAR REACTION ON THE DYNAMICALLY CHANGING SURFACE OF A BODY-CENTERED METAL CRYSTAL
E.A. Cherezov, E.V. Kovalev, V.I. Elokhin, A.V. Myshlyavtsev*,**
(*Institute of Hydrocarbons Processing, Omsk, Russia; **Omsk State Technical University, Omsk, Russia)
Kinet. Catal., 47(4) (2006) pp. 469-480.
A statistical lattice model has been constructed for the surface of a body-centered cubic (bcc) crystal whose morphology varies under the action of external factors (temperature and adsorbate coverage). Monomolecular and dissociative bimolecular adsorption on the bcc crystal surface has been investigated. In this model, adsorption smoothens the originally rough surface owing to adsorbate molecules stabilizing their flat adsorption areas, as distinct from adsorption on the primitive cubic lattice. The model differs from the models with invariable surface morphology in that the number of its accessible adsorption sites is variable and depends on external conditions. The kinetics of a catalytic reaction proceeding by the Langmuir–Hinshelwood mechanism have been studied for the (100) face of a bcc crystal whose morphology varies under the action of the reaction medium.
ON THE PORE SIZE DISTRIBUTIONS OF CARBONACEOUS CATALYSTS AND ADSORBENTS
D.K. Efremov, V.A. Drozdov*
(*Institute of Hydrocarbons Processing, Omsk, Russia)
Chem. Sustain. Devel., 14(6) (2006) pp. 565-569. The modeling of a low temperature nitrogen adsorption in graphite mesopores with rectangular sections having the aspect ratio of the side lengths more than 7:1 has been executed by using the grand canonical Monte Carlo (GCMC) method. The adsorption branches of obtained GCMC isotherms were processed with the purpose of calculation of the formal pore size distributions (PSDs) by the nonlocal density functional theory (NLDFT) and Derjaguin- Broekhoff-de Boer (D-BdB) method. It is shown that NLDFT underestimates the sizes of the model rectangular mesopores though gives good estimations of specific surface area and volume of the pores. Also, it is shown that D-BdB method very strongly underestimates specific surface area and overestimates total volume of pores. PSDs obtained from D-BdB method have a very wide distributive interval of apparent sizes and brightly expressed bimodal forms. Such completely wrong information about the size of the investigated model pores is a consequence of the macroscopic assumption of the D-BdB theory about the constancy of the capillary condensate density in pores at various pressures.
COMBINED IN SITU XPS AND PTRMS STUDY OF ETHYLENE EPOXIDATION OVER SILVER
V.I. Bukhtiyarov, A.I. Nizovskii, H. Bluhm*, M. Hävecker*, E. Kleimenov*,
A. Knop-Gericke*, R. Schlögl*
(*Fritz-Haber-Institut der MPG, Berlin, Germany)
J. Catal., 238(2) (2006) pp. 260-269.
Ethylene epoxidation over silver was investigated by combined in situ X-ray photoelectron spectroscopy (XPS) and proton-transfer reaction mass spectrometry (PTRMS) at 300–520 K and 0.07–1 mbar. Ethylene oxide was present among the reaction products at T ≥ 420 K and p ≥ 0.3 mbar. The catalytically active surface contains two oxygen species – nucleophilic and electrophilic oxygen. The observed correlation between the abundance of electrophilic oxygen and the yield of ethylene oxide expressed as C2H4O partial pressure indicates that namely this oxygen species oxidizes ethylene to ethylene oxide. Opposite trend is observed for nucleophilic oxygen: the higher is the abundance of this species, the lower is the yield of ethylene oxide. This result is in line with the known fact that because of its oxidic nature, nucleophilic oxygen is active in total oxidation of ethylene to CO2 and H2O. The low activity of silver at T < 420 K is caused by the presence of carbonates and carbonaceous residues at the silver surface that reduce the available silver surface area for the catalytic reaction. Reduction of the surface area available for the formation of active species due to accumulation of the embedded oxygen species also explains the decreased rate of ethylene oxide formation with time observed for T ≥ 470 K.
STRUCTURE OF THE ACTIVE COMPONENT AND CATALYTIC PROPERTIES OF CATALYSTS PREPARED BY THE REDUCTION OF LAYERED NICKEL ALUMINOSILICATES
A.A. Khassin, T.M. Yurieva, V.V. Kaichev, V.I. Zaikovskii, M.P. Demeshkina, T.P. Minyukova, N.A. Baronskaya, V.I. Bukhtiyarov, V.N. Parmon
Kinet. Catal., 47(3) (2006) pp. 412-422.
The reduction of Ni–Mg aluminosilicates with the amesite structure was studied using thermogravimetry, high-resolution electron microscopy, XPS, and XRD. It was found that the reduction with hydrogen at 920 K resulted in the formation of nickel particles coated with a difficult-to-reduce amorphous oxide shell. The reduced samples were incapable of chemisorbing oxygen; however, they exhibited a high adsorption capacity for hydrogen. The Ni core–oxide shell decorated particles were highly active in steam methane reforming and CO hydrogenation reactions. At the same time, they were inactive in the formation of graphite-like carbon in both methane decomposition and CO disproportionation.
THE NATURE OF ACTIVE SITES IN Pt PROMOTED GaZSM-5 CATALYSTS
A.L. Lapidus*, M.N. Mikhailov*, A.A. Dergachev*, G.M. Zhidomirov, I.V. Mishin*
(*Zelinsky Institute of Organic Chemistry, Moscow, Russia)
React. Kinet. Catal. Lett., 87(2) (2006) pp. 249-254.
Activity and selectivity of Pt-promoted GaZSM-5 catalysts in the aromatization of ethane were studied. XRD indicated that high temperature treatment of the Pt promoted GaZSM-5 zeolites results in the formation of bimetallic GaPt clusters located on the inner surface of zeolites. Both experimental results and calculations suggest that the clusters containing Ga and Pt atoms stabilized in cationic positions are characterized by an increased activity and selectivity in the dehydrogenation of ethane.
MECHANISM STUDIES OF THE CONVERSION OF 13C-LABELED n-BUTANE ON ZEOLITE H-ZSM-5 STUDIED BY 13C MAGIC ANGLE SPINNING NMR SPECTROSCOPY AND GC-MS ANALYSIS
M.V. Luzgin, A.G. Stepanov, S.S. Arzumanov, V.A. Rogov, V.N. Parmon, W. Wang*, M. Hunger*, D. Freude**
(*Institute of Chemical Technology, University of Stuttgart, Stuttgart, Germany; **Leipzig University, Leipzig, Germany)
Chem. Eur. J., 12(2) (2006) pp. 457-465.
13C MAS NMR spectroscopy shows that the conversion of the selectively 13C-labeled n-butane on zeolite H-ZSM-5 proceeds at 430–470 K via two pathways: (i) a scrambling of the selective 13C-label in the n-butane molecule and (ii) oligomerization- cracking and a conjunct polymerization. The latter two processes produce isobutane and propane simultaneously with the alkyl-substituted cyclopentenyl cations (CPC) and condensed aromatics. In situ 13C MAS NMR and complementary ex situ GC-MS data provide evidence for a monomolecular mechanism of the 13C-label scrambling, whereas both isobutane and propane are formed via an intermolecular pathways of oligomerization-cracking and a conjunct polymerization. According to 13C MAS NMR kinetic measurements, the 13C-label scrambling as well as the formation of isobutane and propane proceed with nearly the same activation energies (Ea = 75 kJ mol-1 for the scrambling and 71 kJ mol-1 for isobutane and propane formation). This can be rationalized in terms of an intermolecular hydride transfer between primarily initiated carbenium ion and n-butane to be the rate-determining stage of the n-butane conversion on zeolite H-ZSM-5.
1H MAS NMR MONITORING OF THE 13C-LABELED CARBON SCRAMBLING FOR PROPANE IN ZEOLITE H-ZSM-5
A.G. Stepanov, S.S. Arzumanov, H. Ernst*, D. Freude*
(*Leipzig University, Leipzig, Germany)
Chem. Phys. Lett., 420(4-6) (2006) pp. 574-576.
It has been demonstrated that 1H MAS NMR spectroscopy can be used as a tool for in situ monitoring the reaction kinetics of 13C-labeled carbon scrambling in alkane molecules adsorbed on zeolite catalysts at the reaction temperature of 540–570 K. The accuracy of the results and the time resolution are improved compared to 13C MAS NMR spectroscopy.
ASYMMETRIC OXIDATION OF SULFIDES WITH H2O2 CATALYZED BY TITANIUM COMPLEXES WITH AMINOALCOHOL DERIVED SCHIFF BASES
K.P. Bryliakov, E.P. Talsi
J. Mol. Catal., 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.
ACTIVE OXYGEN IN SELECTIVE OXIDATION CATALYSIS
G.I. Panov, K.A. Dubkov, E.V. Starokon
Catal. Today, 117(1-3) (2006) pp. 148-155.
The paper reviews literature data related to oxygen species available on the surface of metal oxides and their possible role in selective oxidation. With some reservations, one may conclude that the main concept accepted presently in oxidation catalysis assumes that selective oxidation is provided by strongly bonded lattice oxygen, while the full oxidation is provided by weakly bonded reactive oxygen. Recent studies on the oxidation mechanism over FeZSM-5 zeolites with N2O give ground to reconsider this concept in order to integrate the earlier suggested radical oxygen idea, which supposes an important role of O− radicals in selective oxidation. This highly reactive oxygen species can be considered as a powerful tool for activation of organic molecules.
PLANAR DEFECT OF THE NANO-STRUCTURED ZINC OXIDE AS THE SITE FOR STABILIZATION OF THE COPPER ACTIVE SPECIES IN Cu/ZnO CATALYSTS
A.A. Khassin, V.V. Pelipenko, T.P. Minyukova, V.I. Zaikovskii, D.I. Kochubey, T.M. Yurieva
Catal. Today, 112(1-4) pp. 143-147.
The catalytic activity of CuZn catalysts in the synthesis of methanol is related to those reduced Cu species, which originate from the CuxZn1−xO solid solution of wurtzite-like structure. Copper cations in the CuxZn1−xO solid solution are localized in the extended stacking faults of the ZnO lattice. Copper sites could be supposedly described as the product of introducing (OH) Cu (OH) to the planar defects of zinc oxide structure. Hydroxyl groups stabilize the planar defects of ZnO. The process of the samples reduction leads to the formation of flat Cu0 particles over the surface of zinc oxide. The planar defects of ZnO structure are preserved in the reduced state. During the reoxidation, copper atoms return back to the extended stacking faults of ZnO as the tape-like clusters of flat-square coordinated copper cations.
AMMOXIDATION OF ETHANE ON V-Mo-Nb OXIDE CATALYSTS
V.M. Bondareva, T.V. Andrushkevich, G.I. Aleshina, L.M. Plyasova, L.S. Dovlitova, O.B. Lapina, D.F. Khabibulin, A.A. Vlasov
React. Kinet. Catal. Lett., 87(2) (2006) pp. 377-386.
Catalytic and physicochemical properties of V-Mo-Nb oxide catalysts (V0.3Mo1Nbx, where x = 0.05, 0.15, 0.22, 0.27) have been studied in the reaction of ethane ammoxidation. An increase in the Nb content in the samples is accompanied by an increase in the catalytic activity and selectivity to acetonitrile. It was established that a triple Mo5O14- like phase with a variable composition (V0.23±0.3Mo1Nbx, where х = 0.2÷0.37) acts as an active component in the catalyst.
THE FORMATION OF AN ACTIVE COMPONENT IN V-Mo-Nb-O CATALYSTS OF ETHANE OXIDATION AND AMMOXIDATION
V.M. Bondareva, T.V. Andrushkevich, G.I. Aleshina, R.I. Maksimovskaya, L.M. Plyasova, L.S. Dovlitova, E.B. Burgina
React. Kinet. Catal. Lett., 88(1) (2006) pp. 183-192.
A genesis of an active component in V-Mo-Nb oxide catalysts for the oxidation and ammoxidation of ethane was studied. It was shown that the mixing of the aqueous solutions of initial reactants leads to the formation of MoV complexes in solution and is accompanied with the formation of a sediment of a binary Nb-Mo compound. The latter is the base for formation of the active component phase (a triple V-Mo-Nb compound with a variable composition with Mo5O14-like structure) during the subsequent treatment in air flow at 400°С.
PROPERTIES AND DEACTIVATION OF THE ACTIVE SITES OF AN MoZSM-5 CATALYST FOR METHANE DEHYDROAROMATIZATION: ELECTRON MICROSCOPIC AND EPR STUDIES
V.I. Zaikovskii, A.V. Vosmerikov*, V.F. Anufrienko, L.L. Korobitsyna*, E.G. Kodenev, G.V. Echevsky, N.T. Vasenin, S.P. Zhuravkov**, E.V. Matus, Z.R. Ismagilov, V.N. Parmon
(*Institute of Petroleum Chemistry, Tomsk, Russia; **Institute of Strength Physics and Materials Science, Tomsk, Russia)
Kinet. Catal., 47(3) (2006) pp. 389-394.
The MoZSM-5 (4.0 wt % Mo) catalyst has been characterized by high-resolution transmission electron microscopy, EDXA, and EPR. Two types of molybdenum-containing particles are stabilized in the catalyst in the course of nonoxidative methane conversion at 750°C. These are 2- to 10-nm molybdenum carbide particles on the zeolite surface and clusters smaller than 1 nm in zeolite channels. According to EPR data, these clusters contain the oxidized molybdenum form Mo5+. The surface Mo2C particles are deactivated at the early stages of the reaction because of graphite condensation on their surface. Methane is mainly activated on oxidized molybdenum clusters located in the open molecular pores of the zeolite. The catalyst is deactivated after the 420-min-long operation because of coke buildup on the zeolite surface and in the zeolite pores.
CATALYTIC PROPERTIES AND ELECTRONIC STRUCTURE OF COPPER IONS IN Cu-ZSM-5
S.A. Yashnik, Z.R. Ismagilov, V.F. Anufrienko
Catal. Today, 110(3-4) (2005) pp. 310-322.
The effect of ion exchange conditions, such as Si/Al ratio, precursor copper salt, pH and concentration of the solution, on the catalytic activity in SCR of NO by propane and on the electronic state of copper ions in Cu-ZSM-5 has been studied. The NO conversion in NO SCR by C3H8 has been found to reach a maximum value at Cu/Al ratio about 0.37-0.4 and remain constant at higher Cu/Al. ESR and UV-vis DR spectroscopy have been used to elucidate stabilization conditions of copper ions in Cu-ZSM-5 zeolites as isolated Cu2+ ions, chain copper oxide structures and square-plain oxide clusters. The ability of copper ions for reduction and reoxidation in the chain structures may be responsible for the catalytic activity of Cu-ZSM-5. These transformations of copper ions are accompanied by the observation of intervalence transitions Cu2+-Cu+ and CTLM of the chain structures in the UV-vis spectra.
MECHANISM OF β-PICOLINE OXIDATION TO NICOTINIC ACID ON V-Ti-O CATALYST AS STUDIED BY IN SITU FTIR
G.Ya. Popova, T.V. Andrushkevich, Yu.A. Chesalov, E.V. Ovchinnikova
React. Kinet. Catal. Lett., 87(2) (2006) pp. 387-394.
In situ FTIR spectroscopy was used to study the interaction of β-picoline with the surface of a V-Ti-O catalyst in the temperature range of 120–300°C. β-Picoline was found to react with the Lewis acid sites of the catalyst to form a nitrogen coordinated complex. This complex turns into an aldehyde-like complex at 150–250°C and then into a nicotinate, which is a direct precursor of nicotinic acid.
COMPOSITE MECHANISM OF THE CATALYTIC HYDROGENATION OF UNSATURATED HYDROCARBONS ON HYDRIDED MAGNESIUM INTERMETALLIDES
V.V. Molchanov, V.V. Goidin, R.A. Buyanov
Kinet. Catal., 47(5) (2006) pp. 744-746.
Two temperature ranges are distinguished in the catalytic hydrogenation of unsaturated hydrocarbons on magnesium intermetallide hydrides. In the lower temperature range, the reaction proceeds by a composite mechanism, as is indicated by the fact that the rate of the catalytic hydrogenation of ethylene, n-butenes, and butadiene is equal to the rate of the reduction of these hydrocarbons with hydride hydrogen. It is assumed that, at higher temperatures, the reaction proceeds by a heterogeneous– homogeneous mechanism.
NOx SCR BY DECANE AND PROPYLENE ON Pt + Cu/Zr-PILLARED CLAYS IN REALISTIC FEEDS: PERFORMANCE AND MECHANISTIC FEATURES VERSUS STRUCTURAL SPECIFICITY OF NANOSIZED ZIRCONIA PILLARS
V.A. Sadykov, T.G. Kuznetsova, V.P. Doronin*, R.V. Bunina, G.M. Alikina, L.Ch. Batuev, V.A. Matyshak**, A.Ya. Rozovskii***, V.F. Tretyakov***, T.N. Burdeynaya***, V.V. Lunin****, J. Ross*****
(*Institute of Hydrocarbons Processing, Omsk, Russia; **Semenov Institute of Chemical Physics, Moscow, Russia; ***Topchiev Institute of Petrochemical Synthesis, Moscow, Russia; ****Lomonosov Moscow State University, Moscow, Russia; *****The Limerick University, Limerick, Ireland)
Catal. Today, 114(1) (2006) pp. 13-22.
Pt + Cu-loaded ZrPILC tested in the reactions of NOx selective catalytic reduction by propylene and decane in realistic feeds with a high content of water, oxygen and an admixture of SO2 demonstrated promising performance at high space velocities (up to 100 000 h−1) in the temperature range of 150–400°C. A strong promoting effect of water, oxygen and the catalyst presulfation on the degree of NOx conversion into N2 was revealed. The specificity of these catalysts action in realistic feeds was explained by taking into account the textural, structural and surface features of zirconia-pillared clays as well as the mechanism of NOx HC SCR reaction including participation of strongly bound species in key stages.
REACTION PATHS OF THE FORMATION AND CONSUMPTION OF NITROORGANIC COMPLEX INTERMEDIATES IN THE SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES WITH PROPYLENE ON ZIRCONIA-PILLARED CLAYS ACCORDING TO IN SITU SPECTROSCOPIC DATA
V.A. Matyshak*, V.F. Tret’yakov**, K.A. Chernyshev*, T.N. Burdeinaya**, V.N. Korchak*, V.A. Sadykov
(*Semenov Institute of Chemical Physics, Moscow, Russia; **Topchiev Institute of Petrochemical Synthesis, Moscow, Russia)
Kinet. Catal., 47(5) (2006) pp. 747-755.
It was found that the adsorption and catalytic properties of nanosized ZrO2 particles as the pillar constituents of ZrO2-pillared clay and bulk ZrO2 are essentially different. The interaction of NO with the surface of bulk ZrO2 resulted in the formation of three types of nitrate complexes. Only two nitrate species were formed on ZrO2-pillared clay (the monodentate species was absent). Only an acetate complex was formed in the interaction of a mixture of propylene and oxygen with the surface of bulk ZrO2, whereas an isopropoxide complex was the main propylene activation species on ZrO2-pillared clay. On the surface of ZrO2-pillared clay, isopropoxide and nitrate intermediates formed a complex structurally similar to adsorbed dinitropropane. On the surface of bulk ZrO2, acetate and monodentate nitrate complexes formed a complex structurally similar to adsorbed nitromethane. The dinitropropane complex on ZrO2-pillared clay was consumed in reactions with surface nitrates. The decomposition reaction of a dinitropropane compound with the formation of acetate complexes and ammonia predominated on the surface containing no nitrate complexes in the absence of NO + O2 from a gas phase. The found differences in reactant activation species and their thermal stabilities explained differences in the activities of bulk ZrO2 and nanosized ZrO2 particles as pillars in pillared clay in the course of the selective catalytic reduction of nitrogen oxides with propylene in an excess of oxygen.
ROLE OF NITROGEN DIOXIDE IN THE OXIDATION OF DIESEL SOOT ON PROMOTED MIXED CATALYSTS WITH FLUORITE AND PEROVSKITE STRUCTURES
V.A. Matyshak*, V.A. Sadykov, T.G. Kuznetsova, A.A. Ukharskii*, T.I. Khomenko*, M.Ya. Bykhovskii*, O.N. Sil’chenkova*, V.N. Korchak*
(*Semenov Institute of Chemical Physics, Moscow, Russia)
Kinet. Catal., 47(3) (2006) pp. 400-411.
The oxidation of soot on catalysts with the perovskite and fluorite structures (including platinum- promoted catalysts) in the presence and in the absence of NO2 was studied using in situ IR spectroscopy and temperature-programmed techniques (TPR, TPD, and TPO). It was found that, as a rule, the temperature of the onset of soot oxidation considerably decreased upon the addition of NO2 to a flow of O2/N2, whereas the amount of oxygen consumed in soot oxidation considerably increased. To explain these facts, it was hypothesized that the initiation of soot combustion in the presence of NO2 was related to the activation of the NO2 molecule through the formation (at a low temperature) and decomposition (at a high temperature) of nitrate structures on the catalyst. Superequilibrium amounts of NO2 resulted from the decomposition of nitrate complexes immediately on the catalyst for soot combustion. Based on a comparison between catalyst activities and data obtained by TPR and the TPD of oxygen, a conclusion was drawn that the presence of labile oxygen in the catalyst is a necessary but insufficient condition for the efficient occurrence of a soot oxidation reaction in the presence of NO2. The introduction of platinum as a constituent of the catalyst increased the amount of labile oxygen and, as a consequence, increased the amount of highly reactive nitrate complexes. As a result, this caused a decrease in the temperature of the onset of soot combustion.
REACTION PATHS OF THE FORMATION AND CONSUMPTION OF NITROORGANIC COMPLEX INTERMEDIATES IN THE SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES WITH PROPYLENE ON ZIRCONIUM DIOXIDE ACCORDING TO IN SITU FOURIER TRANSFORM IR SPECTROSCOPIC DATA
V.A. Matyshak*, V.F. Tret’yakov**, K.A. Chernyshev*, T.N. Burdeinaya**, V.N. Korchak*, V.A. Sadykov
(*Semenov Institute of Chemical Physics, Moscow, Russia; **Topchiev Institute of Petrochemical Synthesis, Moscow, Russia)
Kinet. Catal., 47(4) (2006) pp. 593-602.
Nitrate, acetate, and nitroorganic complexes were detected on the surface of ZrO2 under the reaction conditions of nitrogen oxide reduction with propylene using Fourier transform IR spectroscopy. The nitroorganic complex was formed in the reaction between acetate and nitrate complexes by the replacement of the carboxyl group in the acetate complex by the nitro group. Monodentate nitrate was the most reactive species in this process. The adsorption of various nitroorganic substances was studied. It was found that the nitroorganic complex was structurally analogous to the nitromethane molecule bound to the surface through the nitro group. The experimental data led to a conclusion that nitroorganic compounds were subsequently consumed in reactions with nitrate complexes. In this surface reaction, monodentate nitrate was also the most reactive species. The presence of oxygen had no effect on the consumption of the nitroorganic complex.
AMMONIA OXIDATION ON Pt(410)
C.J. Weststrate*, J.W. Bakker*, E.D.L. Rienks*, C.P. Vinod*,**, A.V. Matveev, V.V. Gorodetskii, B.E. Nieuwenhuys*,**
(*Leiden University, Leiden, The Netherlands; **Technische Universiteit Eindhoven, Schuit Institute of Catalysis, Eindhoven, The Netherlands)
J. Catal., 242(1) (2006) pp. 184-194.
The adsorption of both O2 and NH3 on Pt(410) was studied using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Molecular NH3 desorbed from Pt(410) between 100 and 450 K, and dissociation was not observed. Radiation (X-Rays, electrons) induced NH3ad dissociation, and as a result several dissociation products (NH2ad, NHad, and Nad) were observed in the N 1s core-level spectrum. NHad is a rather stable dissociation product that starts to dehydrogenate above 350 K. The Nad and Had formed in this process desorbed on formation (as N2 and H2). Both molecular and dissociative O2 adsorption were observed after the surface was exposed to O2(g) at 100 K. Molecularly adsorbed O2 desorbed below 200 K, whereas atomic oxygen desorbed (as O2) between 600 and 900 K, in two distinct desorption peaks. In the O 1s core-level spectrum, both molecular O2 and two different types of Oad were distinguished. NH3ad dissociation was observed on an oxygen-presaturated surface. The NH3ad oxy-dehydrogenation started at 150 K. NOad and NO(g) were also observed, but only during experiments in which an excess of Oad was available. NOad desorbed/decomposed between 400 and 500 K. For the steady-state ammonia oxidation reaction, N2 and H2O were the major products at low temperatures, whereas the selectivity toward NO and H2O changed at higher temperatures. This selectivity change can be attributed to changes in surface composition.
SELECTIVE, C,C-DOUBLE BOND REDUCTION OF α,β-UNSATURATED CARBONYL COMPOUNDS WITH CYCLOHEXANE USING ZEOLITES
K.Yu. Koltunov, St. Walspurger*, J. Sommer*
(*Université L. Pasteur, Strasbourg, France)
J. Mol. Catal. A: Chem., 245(1-2) (2006) pp. 231-234.
Selective ionic hydrogenation of α,β-unsaturated carbonyl compounds with alkanes (cyclohexane and others) was previously known to proceed only in superacidic conditions due to the necessity of dicationic, superelectrophilic activation of the enones. In present paper it is disclosed that H-form zeolites with acidity well below superacidity, are able however to induce the reduction of α,β-unsaturated carbonyl compounds with cyclohexane in strong analogy to the “parent”, superacid mediated reactions. The probable interpretation of these results in terms of highly electrophilic (superelectrophilic) intermediates on the solid is discussed.
SUPERACIDIC ACTIVATION OF MALEIMIDE AND PHTHALIMIDE AND THEIR REACTIONS WITH CYCLOHEXANE AND AROMATIC COMPOUNDS
K.Yu. Koltunov, G.K. Prakash*, R. Surya*, O. Golam*, A. George*
(*University of Southern California, Los Angeles, California, USA)
Eur. J. Org. Chem., 21 (2006) pp. 4861-4866.
When activated in the CF3SO3H/SbF5 acid system maleimide (1) and phthalimide (2) undergo selective ionic hydrogenation with cyclohexane to give 1,5-dihydropyrrol-2-one (3) and phthalimidine (11), respectively. When treated with aluminum halides, N-phenylmaleimide (4) reacts with cyclohexane to give N-phenylsuccinimide (5), whereas 2 still gives 11. Imide 1 also condenses with benzene in trifluoromethanesulfonic acid (CF3SO3H) to give 1,5-dihydro-5,5-diphenylpyrrol-2-one (7) as the major product. However, in the presence of aluminum halides 1 reacts with benzene, toluene, and o-dichlorobenzene to give 3-arylsuccinimides 8-10, respectively. Imide 2 reacts with benzene under the influence of trifluoromethanesulfonic acid as well as aluminum halides to yield 3,3-diphenylphthalimidine (12). The mechanism of these reactions, with potential involvement of superelectrophilic dicationic intermediates, is discussed.
ISOTOPE EXCHANGE BETWEEN NO AND H2O ON A PLATINUM-CONTAINING CATALYST BASED ON FIBERGLASS
E.M. Sadovskaya, A.P. Suknev, A.V. Toktarev, L.G. Simonova, E.A. Paukshtis, B.S. Bal’zhinimaev
Kinet. Catal., 47(1) (2006) pp. 131-138.
The dynamics of 18O isotope exchange between NO or H2O and a catalyst and the dynamics of 18O label transfer from NO to H2O have been studied under conditions of sorption–desorption equilibrium. The occurrence of a reaction of oxygen exchange between NO and water sorbed in the bulk of the catalyst was detected. This reaction occurs at platinum sites with the participation of acid sites of the glass matrix. The rate constants of the reaction of NO with platinum sites and the diffusion coefficients of water in the bulk of the glass matrix are evaluated.
13C NMR STUDIES OF IZOMERIZATION OF D-GLUCOSE IN AN AQUEOUS SOLUTION OF Ca(OH)2. THE EFFECT OF MOLECULAR OXYGEN
A.N. Simonov, O.P. Pestunova, L.G. Matvienko, V.N. Parmon
Russ. Chem. Bull., 8 (2005) pp. 1967-1972.
Isomerization of D-glucose to fructose and mannose in aqueous solutions of Ca(OH)2 with the initial pH 11.4 in a temperature interval of 20-90°С was studied by 13C NMR spectroscopy in the presence and absence of dissolved oxygen. In the presence of oxygen, the apparent equilibrium isomerization constant is much lower than that in the absence of oxygen. This is related to the oxidation of monosaccharides to formic and aldonic acids, a decrease in the pH of solutions, and cessation of isomerization at pH < 9.
NMR STUDIES OF MOLECULAR MOTION OF ULTRADISPERSED POLYTETRAFLUOROETHYLENE
V.M. Buznik, A.I. Livshits*, M. Ol’shevskii**, A.R. Semenov***, N.A. Sergeev**
(*Institute of Chemistry and Chemical Technology, Krasnoyarsk, Russia; **Institute of Physics of Szczecin University, Poland; ***Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Struct. Chem., 47(4) (2006) pp. 668-673.
Molecular motion in ultradispersed polytetrafluoroethylene obtained by special gas-phase technology has been studied experimentally and theoretically based on a temperature dependence of the second moment of 19F NMR spectra and the time of spin-lattice relaxation. The results of observations are interpreted as the consequence of reorientation motion of CF2 groups around the axis of macromolecules at low temperature and of translational motion of macromolecules in the high temperature region. Qualitative differences from the molecular motion in industrial polytetrafluoroethylene (teflon-4) were detected and parameters of dynamic processes determined.
SOLID STATE MULTINUCLEAR NMR STUDIES OF NANOSTRUCTURED THIN OXIDE FILMS
O.B. Lapina
Chinese J. Light Scatt., 17(10) (2005) pp. 287-288.
Detailed knowledge of the molecular structure and electronic structures of surface thin oxide films, their active sites and their corresponding reactivity/selectivity relationships are the critical fundamental information that is necessary for the molecular engineering of active surface oxide species for specific catalytic applications. Modern solid state NMR techniques became a keystone technique for characterization of local structure of quadrupolar nuclei (51V, 93Nb, 27Al, 45Sc, 17O) in different oxide systems. Herein the current state of solid state NMR techniques in their applications to thin oxide films is discussed.
129Xe NMR STUDY OF PITCH-BASED ACTIVATED CARBON MODIFIED BY AIR OXIDATION/PYROLYSIS CYCLES: A NEW APPROACH TO PROBE THE MICROPORE SIZE
K.V. Romanenko, X. Py*, J.-B. d’Espinose de la Caillerie**, O.B. Lapina, J. Fraissard**
(*Ecole Supérieure de Physique et de Chimie Industrielles, Paris Cedex, France; **Processes Materials and Solar Energy Laboratory, Perpignan Cedex, France)
J. Phys. Chem. B., 110(7) (2006) pp. 3055-3060
129Xe NMR has been used to study a series of homologous activated carbons obtained from a KOH activated pitch-based carbon molecular sieve modified by air oxidation/pyrolysis cycles. A clear correlation between the pore size of microporous carbons and 129Xe NMR of adsorbed xenon is proposed for the first time. The virial coefficient δXe-Xe arising from binary xenon collisions varied linearly with the micropore size and appeared a better probe of the microporosity than the chemical shift extrapolated to zero pressure. This correlation related to SFD (single file diffusion) phenomenon indicated that the xenon collision frequency increases with increasing micropore size. The chemical shift has been shown to vary very weakly with temperature (less than 9 ppm) for xenon trapped inside narrow and wide micropores. This is indicative of smooth xenon – surface interaction potential.
ACTIVATION OF rac-Me2Si(ind)2ZrCl2 BY METHYLALUMOXANE MODIFIED BY ALUMINUM ALKYLS: AN EPR SPIN-PROBE, 1H NMR, AND POLYMERIZATION STUDY
K.P. Bryliakov, N.V. Semikolenova, V.N. Panchenko, V.A. Zakharov, H.H. Brintzinger*, E.P. Talsi
(*University of Konstanz, Konstanz, Germany)
Macromol. Chem. Phys., 207(3) (2006) pp. 327-335.
Solutions containing mixtures of methylalumoxane (MAO) and iBu3Al give rise to 1H NMR signals indicative of the presence of the mixed alkyl aluminum dimers iBu2Al(µ-Me)2AliBu2 and of mixed clusters of the type (AlMe(1 + 2x - y)iBuyO(1 - x))n. These mixed clusters, as well as related species present in solutions containing either MAO-Et3Al or commercially available modified MAO (MMAO), appear to have stronger Lewis acidic sites and greater hydrodynamic radii than comparable clusters present in solutions of MAO alone, as judged from EPR signals observed in these solutions upon addition of TEMPO. When (SBI)ZrCl2 (SBI = rac-Me2Si(ind)2) is reacted with one of these mixed activator reagents, the mixed heterobinuclear cation [(SBI)Zr(µ-Me)2AlMeiBu]+ appears to be formed, together with its methyl counterpart [(SBI)Zr(µ-Me)2AlMe2]+, which is normally predominant in the (SBI)ZrCl2/MAO system at [Al]MAO/[Zr] ratios above 100. In the presence of iBu3Al, the formation of heterobinuclear cations is suppressed in favor of ion pairs containing the cation [(SBI)ZrMe] in contact with a (MAO-TIBA)-derived counter anion. The greater reactivity of these contact- ion pairs, as compared to the normally prevalent AlMe3 adducts, as well as an increased Lewis acidity of MMAO, and the ensuing decreased coordination ability of the [Me-(MAO-TIBA)]- counter ion as compared to [Me-MAO]-, are likely to contribute to the positive effects of TIBA additions on the co-catalytic activity of MAO.
NMR IMAGING AS A TOOL FOR STUDYING MASS TRANSPORT IN POROUS MATERIALS
I.V. Koptyug*, A.A. Lysova, A.V. Matveev*, L.Yu. Ilyina*, R.Z. Sagdeev*, V.N. Parmon
(*International Tomography Center, Novosibirsk, Russia)
In “Fluid Transport in Nanoporous Materials”, NATO Science Series II: Mathematics, Physics and Chemistry, vol. 219, Eds. W.C. Conner, J. Fraissard, Springer, 2006, pp. 353-374.
Modern magnetic resonance is an extremely broad field of scientific research, which embraces a vast variety of experiments and techniques. To better define the place of NMR imaging in magnetic resonance, it might be advantageous to consider the majority of the magnetic resonance (MR) experiments as being performed in a multidimensional space of frequencies, spatial coordinates and time. Each particular MR experiment then addresses a certain subset of the parameter space. For instance, 2D (two- dimensional) NMR spectroscopy utilizes two frequency coordinates, while diffusion studies with PFG (pulsed field gradient) NMR use one spatial and one temporal coordinates, etc. NMR imaging (MRI) experiments can thus be defined as those which involve at least one spatial coordinate. Since the encoding of a spatial coordinate can be added to almost any MR experiment, this gives an infinite number of possibilities for performing MRI studies.
COMPLEXES OF THE PROTON AND ITS HYDRATES WITH CARBAMOYLPHOSPHINE OXIDE IN WET DICHLOROETHANE SOLUTIONS
E.S. Stoyanov, I.V. Smirnov*, M.A. Fedotov
(*Khlopin Radium Institute, St. Petersburg, Russia)
J. Phys. Chem. A, 110(30) (2006) pp. 9505-9512.
To better understand the complex equilibria involved in the UNEX process for acidic solvent extraction of radionuclides, the interaction of a carbamoylphosphine oxide ligand (L) with the proton of hydrated chlorinated cobalt(III)dicarbollide acid, H[Co(C2B9H8Cl3)2], has been studied in wet 1,2-dichlorethane (DCE) solution using IR and NMR (13C and 31P) spectroscopy. The formation of two groups of complexes has been determined. The first group contains three complexes with 1:1 composition of acid to ligand. The second group of complexes has 1:2 composition in the equilibrium. Within each group, the complexes differ in composition only by the number of incorporated water molecules. The equilibria are both very sensitive to the content of self- associated water in solution and are driven by its concentration, which is unsteady and depends on the solution preparation history. The simultaneous presence of both anhydrous and hydrated proton solvates indicates that the enthalpies of carbamoylphosphine oxide complex formation with H+, H3O+, and H5O2+ are very close to each other.
THE STRUCTURE OF THE H3O+ HYDRONIUM ION IN BENZENE
E.S. Stoyanov, S.P. Hoffmann*, Kee-Chan Kim*, F.S. Tham*, C.A. Reed*
(*University of California, Riverside, California)
J. Am. Chem. Soc., 127(21) (2005) pp. 7664-7665.
Infrared, X-ray structural, 1H NMR, and computational evidence for π-solvation of H3O+ by benzene molecules is presented. A salt with a discrete [H3O·3benzene]+ cation can be isolated using a very weakly interacting carborane counterion, CHB11Cl11-. π-Arene solvation of H3O+ explains the solubility of this salt in benzene solution. Similar results are indicated for the "Zundel-type" H5O2+ ion. These findings suggest structures for the active protonating species when strong acids are used as catalysts in arene solvents containing trace water. They are also relevant to structures that may be present in biological proton transport.
NMR STRUCTURAL ASPECTS OF THE CHEMISTRY OF V, Mo, W POLYOXOMETALATES
M.A. Fedotov, R.I. Maksimovskaya
Russ. J. Struct. Chem., 47(5) 2006) pp. 952-978.
The results of structural investigations of vanadium, molybdenum, and tungsten polyoxoanions (PA) by 17O, 51V, 95Mo, 183W, and heteroatom NMR are generalized in this review. NMR spectroscopy possibilities to determine the structure of PA are discussed. NMR data on PA of different structures compositions nuclei are demonstrated.
TOMOGRAPHY RECONSTRUCTION OF HABITUS OF METAL NANOCRYSTALLS ACCORDING TO PEM DATA
O.G. Abrosimov, A.L. Chuvilin*, E.M. Moroz
(*University of Ulm, Ulm, Germany)
Bull. Russ. Acad. Sci.: Physics, 70(4) (2006) pp. 549-552.
The High Angle Centered Dark Field (HACDF) registration mode has been developed at the Boreskov Institute of Catalysis and used for the first time to acquire angle series of strongly dissipating objects for the further tomographic reconstruction of their spatial structure. Special tomographic holder and gauzes have been developed, the algorithm for equalization of the angle series suggested and applied.
The developed method provides unique potentialities for studying morphological features of nanosized objects.
ELECTRON MICROTOMOGRAPHY: A NEW METHOD FOR STUDYING THE SPATIAL
O.G. Abrosimov, E.M. Moroz, A.L. Chuvilin*
(*University of Ulm, Ulm, Germany)
Kinet. Catal., 47(3) (2006) pp. 464-466.
The spatial arrangement of active component (Pt) particles on the surface of a support (Sibunit globule) has been studied by bright-field electron tomography. A tomographic attachment for a standard specimen holder and tomographic grids have been designed. The tomographic procedure has been refined, and adequate tilt series alignment and tomographic reconstruction algorithms have been chosen. The 3D distribution of the active component in the catalyst grain has been studied: particles hidden in micropores have been directly observed, and the size of the pores connecting internal cavities with the exterior has been estimated.
NEW DATA ON THE STRUCTURE OF FINE ALUMINIUM HYDROXIDE
K.I. Sheffer, D.A. Zyuzin, E.M. Moroz
Bull. Russ. Acad. Sci.: Physics, 70(4) (2006) pp. 1068-1070.
The structure of aluminium hydroxides – pseudoboehmites with various characteristics produced by different methods was studied by method of wide-angle X-ray scattering. In contrast to reference data, it was found that modifications in the structure of pseudoboehmite layers occur via the insertion of additional water molecules.
LOCAL STRUCTURE OF PSEUDOBOEHMITES
E.M. Moroz, K.I. Shefer, D.A. Zyuzin, A.S. Ivanova, E.V. Kulko, V.V. Goidin, V.V. Molchanov
React. Kinet. Catal. Lett., 87(2) (2006) pp. 367-375.
The structure of pseudoboehmite was studied by the method of wide-angle X-ray scattering (WAXS). The samples of pseudoboehmite with various characteristics produced by different methods were examined in order to obtain the most complete information about their structure. In contrast to reference data, it was found that modifications in the structure of pseudoboehmite layers occur via the insertion of additional water molecules.
X-RAY, RAMAN AND FTIRS STUDIES OF THE MICROSTRUCTURAL EVOLUTION OF ZIRCONIA PARTICLES CAUSED BY THE THERMAL TREATMENT
D.A. Zyuzin, S.V. Cherepanova, E.M. Moroz, E.B. Burgina, V.A. Sadykov, V.G. Kostrovskii*, V.A. Matyshak**
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Semenov Institute of Chemical Physics, Moscow, Russia)
Solid State Chem., 179(10) (2006) pp. 2965-2971.
Genesis of the structure of zirconia particles prepared by precipitation of amorphous hydrated zirconia by ammonia from the ZrO(NO3)2 solution followed by a mild hydrothermal treatment (HTT) of precipitate, washing and calcination under air up to 1000°C has been studied by X-ray diffraction (XRD), Raman and FTIRS. As revealed by FTIRS of lattice modes, the local structure of amorphous zirconia subjected to HTT is close to that in μ-ZrO2. This helps to obtain nearly single-phase monoclinic nanozirconia (particle size 5–15 nm) already after a mild calcination at 500°C. Stability of this phase with nanoparticles sizes below the critical value determined by thermodynamic constraints is due to its excessive hydroxylation demonstrated by FTIRS. Dehydroxylation and sintering of these nanoparticles at higher (600–650°C) temperatures of calcination leads to reappearance of the (111) “cubic” reflection in XRD patterns. Modeling of XRD patterns revealed that this phenomenon could be explained by polysynthetic (001) twinning earlier observed by HRTEM.
PROBING THE BRØNSTED AND LEWIS ACIDITY OF Fe-SILICALITE BY FTIR SPECTROSCOPY OF H2 ADSORBED AT 20 K: EVIDENCES FOR THE FORMATION OF Fe3+/H2 AND Fe2+/H2 MOLECULAR ADDUCTS
G. Berlier*, E.N. Gribov, D. Cocina*, G. Spoto*, A. Zecchina*
(*University of Torino, Torino, Italy)
J. Catal., 238(2) (2006) pp. 243-249.
The spectroscopic characterisation of a Fe-silicalite sample in terms of Brønsted and Lewis acidity using H2 as a probe molecule at low temperature (20 K) is reported. At 20 K, H2 is able to form adducts with surface sites present in the internal (and external) surface of zeolites: Brønsted, silanols, and metal ions. The spectroscopic manifestations of the different H2 adducts are found in distinct spectral regions depending on the nature and strength of the adducts: νHH modes of OH-H2 adducts are found in the 4170-4100 cm-1 region, and those of Fex+...H adducts are found in the 4100–3900 cm-1 region. Four distinct Fex+ H2 adducts (at 4050, 4028, 3990, and 3960 cm-1) were formed on extra-framework Fe sites, created by controlled migration of Fe from the framework as a consequence of thermal treatments. The dependence on red–ox treatments of the relative concentration of these sites allowed identification of two Fe2+ and two Fe3+ distinct sites, interacting with H2 mainly by electrostatic forces. The importance of these sites as active species for the selective oxidation of hydrocarbons with N2O is discussed.
VIBRATIONAL AND THERMODYNAMIC PROPERTIES OF Ar, N2, O2, H2 AND Co ADSORBED AND CONDENSED INTO (H, Na)-Y ZEOLITE CAGES AS STUDIED BY VARIABLE TEMPERATURE IR SPECTROSCOPY
E.N. Gribov, D. Cocina*, G. Spoto*, S. Bordiga*, G. Ricchiardi*, A. Zecchina*
(*University of Torino, Torino, Italy)
Phys. Chem. Chem. Phys., 8(10) (2006) pp. 1186-1196.
The adsorption of Ar, H2, O2, N2 and CO on (H,Na)-Y zeolite (Si/Al = 2.9, H+/Na+ ≈ 5) has been studied at variable-temperature (90–20 K) and sub-atmospheric pressure (0–40 mbar) by FTIR spectroscopy. Unprecedented filling conditions of the zeolite cavities were attained, which allowed the investigation of very weakly adsorbed species and of condensed, liquid-like or solid-like, phases. Two pressure regimes were singled out, characterized by: (i) specific interaction at low pressure of the probe molecules (P) with the internal Brönsted and Lewis sites, and (ii) multilayer adsorption at higher pressure. In the case of CO the perturbation of the protonic sites located inside the sodalite cages was also observed. As the molecule is too large to penetrate the sodalite cage, the perturbation is thought to involve a proton jump tunneling mechanism. The adsorption energy for the (HF)OH P (P = Ar, H2, O2, N2 and CO) specific interaction involving the high frequency Brönsted acid sites exposed in the supercages was derived following the VTIR (variable temperature infrared spectroscopy) method described by E. Garrone and C. Otero Arean (Chem. Soc. Rev., 2005, 34, 846).
NEW FRONTIER IN TRANSMISSION IR SPECTROSCOPY OF MOLECULES ADSORBED ON HIGH SURFACE AREA SOLIDS: EXPERIMENTS BELOW LIQUID NITROGEN TEMPERATURE
G. Spoto*, S. Bordiga*, A. Zecchina*, D. Cocina*, E.N. Gribov, L. Regli*, E. Groppo*, C. Lamberti*
(*University of Torino, Torino, Italy)
Catal. Today, 113(1-2) (2006) pp. 65-80.
IR spectroscopy of adsorbed probe molecules is one of the most powerful characterization techniques for the investigation of surface active sites on high surface area materials like oxides and zeolites. In the last 20 years the use of specific IR cells allowing the in situ sample activation, gas dosage and sample cooling down to liquid nitrogen temperature has remarkably improved the number and the quality of the information on the surface structure with respect to the first experiments carried out at room temperature. Commercial cryostats able to reach liquid helium temperatures are available since decades, but the incompatibility of the materials used to reach and confine very low temperatures with the high temperatures usually needed to activate the surfaces of catalysts has prevented for long time the breaking down of the 77 K frontier in IR experiments of species adsorbed on active surface sites. It was recently designed, realized and tested a new experimental set- up able to perform IR experiments in the 15–300 K interval on samples previously activated under vacuum conditions (P < 10-4 Torr, 1 Torr ~ 133.3 Pa), or in the desired atmosphere, up to 1073 K [G. Spoto, E.N. Gribov, G. Ricchiardi, A. Damin, D. Scarano, S. Bordiga, C. Lamberti, A. Zecchina, Prog. Surf. Sci., 76 (2004) 71]. The first results obtained with this innovative instrument will be reviewed and summarized in this work and compared with previous literature results on similar experiments performed at liquid nitrogen temperature. In particular, it will be discussed the adsorption of CO and H2 on MgO and H-SSZ-13 zeolite, and of H2 on Cu+-ZSM-5 zeolite.
INFLUENCE OF COHERENT CONNECTION OF CRYSTALLINE BLOCKS ON THE DIFFRACTION PATTERN OF NANOSTRUCTURED MATERIALS
S.V. Cherepanova, S.V. Tsybula
Z. Kristallogr., suppl_23 (2006) pp. 155-160.
The diffraction effects such as anisotropic broadening of diffraction peaks, their splitting to the relatively broad and narrow components, their shifts and/or the appearance of new ones can result from a coherent connection of nanoblocks. These effects can be mistakenly ascribed to size or strain anisotropy, bimodal size distribution, change in lattice constants and/or the presence of additional phases correspondingly. Developed software provides correct interpretation of the peculiarities of the X-ray diffraction patterns of materials containing planar defects arising from coherent connection of nanoblocks, that is illustrated by several examples. For 1D nanostructured materials, the type and the concentration of the planar defects can be determined on the basis of fitting of the whole pattern. If the microstructure is modulated in more than one direction, only single diffraction peaks can be analysed using the model of 1D disordered crystal.
INTERACTION OF COPPER-BASED SOLID SOLUTIONS WITH LIQUID GALLIUM EUTECTICS
A.I. Ancharov*, T.F. Grigorieva*, S.V. Tsybulya, V.V. Boldyrev*
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Russ. Metallurgy, 2 (2006) pp. 143-146.
The interaction of binary solid solutions with binary gallium eutectics is studied in situ by X-ray diffraction using synchrotron radiation to reveal the sequence of phase formation for the elements that leave a solid solution and a eutectic during the formation of the first intermetallic phase. A comparison of the chemical interactions of the solid solution of tin in copper with the gallium-indium eutectic, the solid solution of indium in copper with the gallium-tin eutectic, and the solid solution of bismuth in copper with these eutectics shows that phase formation during interaction depends on the state of the element (liquid or solid).
MECHANISMS OF Pd(110) SURFACE RECONSTRUCTION AND OXIDATION: XPS, LEED AND TDS STUDY
A.I. Titkov, A.N. Salanov, S.V. Koscheev, A.I. Boronin
Surf. Sci., 600(18) (2006) pp. 4119-4125.
Oxygen interaction with Pd(110) has been studied in a wide range of pressures (Po2=10-6– 100 Pa) and temperatures (T = 400–600 K) by X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and thermal desorption spectroscopy (TDS). The amount of oxygen absorbed by Pd(110) single crystal grows to more than 100 ML when the reaction temperature and the O2 exposure are increased. Several reconstructed and oxide structures are sequentially formed on Pd(110) as the amount of adsorbed and absorbed oxygen increases. During oxygen adsorption (1 x 2) reconstruction occurs and a c(2 x 4) structure is formed on Pd(1 1 0) at θ = 0.5 ML. When the amount of absorbed oxygen increases from 0.5 to 2.0 ML, oxygen penetrates into subsurface Pd layers to the depth exceeding 15–20 Å while retaining the c(2 x 4) structure. When the amount of absorbed oxygen is between 2 and 5 ML, the surface is subjected to reconstruction with the formation of a surface oxide with θ ~ 0.8 that has a complex LEED diffraction pattern. Further increase of the amount of absorbed oxygen beyond 5 ML leads to oxygen location in the subsurface region forming PdO clusters. They gradually grow to form an almost continuous layer composed of PdO clusters.
OXYGEN INTERACTION WITH Pd(110): SURFACE OXIDE FORMATION
A.I. Titkov, A.N. Salanov, S.V. Koscheev, A.I. Boronin
Phys. Low-Dimensional Struct., 2 (2006) pp. 107-118.
Oxygen interaction with Pd(110) has been studied in a wide range of pressures (Ро2 =5x10-7 – 10 Pa) at T = 400 К by X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). When the O2 exposure grows by increasing the treatment time and oxygen pressure from 5x10-7 to 10 Pa, the amount of oxygen absorbed by Pd(110) monocrystal increases up to 4.5 ML. The oxygen coverage increasing to 0.5 ML leads to the formation of the c(2x4) structure on Pd(110). When the amount of absorbed oxygen increases from 0.5 to 2 ML, oxygen penetrates into subsurface Pd layers to the depth more than 15-20 Å whereas the c(2x4) structure is preserved. When the amount of oxygen increases from 2 ML to 4.5 ML a new surface phase is formed on Pd(110) surface. XPS characteristics of this phase were attributed to a surface oxide.
SYNTHESIS OF SILICA POLYPHOSPHATE MATERIALS OF COMPOSITION: – (SiO2)n–(P2O5) m–Ме+
O.V. Magaev*, A.S. Knyazev*, M.A. Malysheva*, A.I. Boronin, O.V. Vodyankina*
(*Tomsk State University, Tomsk, Russia)
Academy Proceed., Physics, 49(3) (2006) pp. 6-9.
X-ray photoelectron spectroscopy (XPS) was used to study catalysts obtained by sol-gel technique for synthesis of Ag catalysts. Peculiarity of these catalysts is formation of active component as Ag nanoparticles directly on the stages of synthesis and subsequent drying and calcination.
STUDYING OF THE POWDERS FOR NONLEADED PASTE FOR HIGH-TEMPERATURE SOLDERING OF COPPER ALLOYS
V.V. Kaichev, V.E. Dyakov*
(*JSC “Novosibirsk Tin Smelter, Novosibirsk, Russia)
Chem. Sustain. Devel., 14(2) (2006) pp. 141-146.
X-ray photoelectron spectroscopy is used to study a series of fine powders of copper alloy with adding of 15 mass % of Sn, 4 mass % of Ni and 5 mass % of P. It is shown that chemical composition of near-surface layer of powder particles of solder depends on the method of preparation and significantly influences on the quality of soldering.
PLASMA DEPOSITION AND PROPERTIES OF SILICON CARBONITRIDE FILMS
T.P. Smirnova*, A.M. Badalyan*, V.O. Borisov*, V.V. Kaichev, L.F. Bakhturova*, V.N. Kichai*, V.I. Rakhlin**, B.A. Shainyan**
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Favorskii Institute of Chemistry, Irkutsk, Russia)
Inorg. Mater., 41(7) (2005) pp. 706-712.
A variety of advanced analytical techniques were used to characterize silicon carbonitride films grown from new volatile nitrogen-rich silyl derivatives of asymmetrical dimethylhydrazine: (CH3)2HSiNHN(CH3)2 (DMDMSH) and Me2Si(NHNMe2)2 (bisDMHDMS). The results demonstrate that the films contain only Si–C, Si–N, and C(sp3)–N bonds, in relative amounts that depend on the molecular structure of the precursor and deposition conditions. The Si–C/[Si–N + C(sp3)–N] ratio is considerably larger in the films grown from DMDMSH. The data obtained by a variety of spectroscopic techniques provide solid evidence that some of the films contain C(sp3)–N bonds, characteristic of superhard materials, and that the films have a complex, framework structure, rather than being a mixture of Si3N4, SiC, and C3N4. The structure of the films depends on the N : Si ratio in the precursor: at N : Si = 2, the films are amorphous and contain nanocrystalline inclusions with a tetragonal structure; at N : Si = 4, the films are purely amorphous. The ability to control the chemical composition and structure of deposits allowed to produce films with various physicochemical and electrical properties.
CHEMICAL VAPOR INFILTRATION METHOD FOR DEPOSITION OF GOLD NANOPARTICLES ON POROUS ALUMINA SUPPORTS
P.P. Semyannikov*, B.L. Moroz, S.V. Trubin*, G.I. Zharkova*, P.A. Pyryaev, M.Yu. Smirnov, V.I. Bukhtiyarov
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Struct. Chem., 47(3) (2006) pp. 458-464.
Knudsen’s effusion method with mass spectral analysis of the composition of the gas phase was used to measure the temperature dependence of the saturated vapor of several (CH3)2AuL chelate complexes and to determine the thermodynamic parameters of their sublimation. Based on the results of this study, conditions for chemical vapor deposition of gold using dimethylgold(III) chelates were chosen. Gold nanoparticles were synthesized by chemical vapor deposition (infiltration) of (CH3)2Au(acac) on porous granules of γ-Al2O3 with subsequent calcination in air at 325°C. Particle size and the chemical state of gold in Au/γ-Al2O3 systems were evaluated by transmission electron microscopy (TEM) and X-Ray photoelectron spectroscopy (XPS). A vapor infiltration procedure is suggested to prepare metallic gold particles ≤ 5 nm in diameter from Au/γ-Al2O3. It is shown that Au/γ-Al2O3 systems obtained by chemical vapor infiltration and containing small gold crystallites possess high catalytic activity in CO oxidation reactions at 40°C.
MODEL CATALYST STUDIES OF THE STRONG METAL-SUPPORT INTERACTION: SURFACE STRUCTURE IDENTIFIED BY STM ON Pd NANOPARTICLES ON TiO2(110)
M. Bowker*, P. Stone**, P. Morrall**, R. Smith**, R. Bennett**, N. Perkins**, R.I. Kvon, C. Pang**, E. Fourre*, M. Hall*
(*Surface Science and Catalysis Group, Cardiff University, Cardiff, UK; **Centre for Surface Science and Catalysis, University of Reading, Reading, UK)
J. Catal., 234(1) (2005) pp. 172-181.
Model catalysts of Pd nanoparticles and films on TiO2(110) were fabricated by metal vapour deposition (MVD). Molecular beam measurements show that the particles are active for CO adsorption, with a global sticking probability of 0.25, but that they are deactivated by annealing above 600 K, an effect indicative of SMSI. The Pd nanoparticles are single crystals oriented with their (111) plane parallel to the surface plane of the titania. Analysis of the surface by atomic resolution STM shows that new structures have formed at the surface of the Pd nanoparticles and films after annealing above 800 K. There are only two structures, a zigzag arrangement and a much more complex “pinwheel” structure. The former has a unit cell containing 7 atoms, and the latter is a bigger unit cell containing 25 atoms. These new structures are due to an overlayer of titania that has appeared on the surface of the Pd nanoparticles after annealing, and it is proposed that the surface layer that causes the SMSI effect is a mixed alloy of Pd and Ti, with only two discrete ratios of atoms: Pd/Ti of 1:1 (pinwheel) and 1:2 (zigzag). It is proposed that it is these structures that cause the SMSI effect.
THE PENETRATION OF INDIUM-GALLIUM MELT COMPONENTS INTO ALUMINUM
M.V. Trenikhin*, A.V. Bubnov*, A.G. Kozlov**, A.I. Nizovskii, V.K. Duplyakin*
(*Institute of Hydrocarbons Processing, Omsk, Russia; **Omsk Department of the Institute of Semiconductor Physics, Omsk, Russia)
Russ. J. Phys. Chem., 80(7) (2006) pp. 1110-1114.
The penetration of indium–gallium melt into aluminum alloys was studied by X-ray fluorescence spectroscopy, X-ray diffraction, and optical microscopy. The X-ray fluorescence data were used to suggest a method for estimating the bulk diffusion coefficient of liquid gallium into grains of polycrystalline aluminum alloys of various brands.
PHYSICOCHEMICAL INVESTIGATION INTO THE SPECIFIC FEATURES OF THE PHASE TRANSFORMATIONS IN ELECTRODEPOSITED NANOCRYSTALLINE OXOTUNGSTATE FILMS
I.Yu. Molina, L.M. Plyasova, A.I. Nizovskii, A.N. Gavrilov*, G.N. Kustova, N.A. Rudina
(*Moscow Lomonosov State University, Moscow, Russia)
Cryst. Rep., 51(suppl. 1) (2006) pp. 130-138.
The structure of oxotungstate films (as-deposited and subjected to heat treatment at temperatures of up to 600°C) prepared through electrodeposition on platinum and gold polycrystalline substrates is investigated using different physicochemical methods. It is shown that the oxotungstate films consist of X-ray amorphous hydrated mixtures of isopoly compounds, predominantly in the form of paratungstates with [H2W12O42]10– anions. The structural transformation with an increase in the temperature in air is accompanied by the loss of water, the transformation of paratungstate anions into more oxidized forms, their destruction, and the crystallization of nonstoichiometric hydroxylated oxide phases.
EXAFS INVESTIGATION OF THE LOCAL ATOMIC STRUCTURE OF Fe-Ge NANOCRYSTALLINE DISORDERED ALLOYS
E.V. Voronina*, G.N. Konygin*, A.N. Deyev*, V.V. Kriventsov, E.P. Yelsukov*
(*Physical- Technical Institute, Izhevsk, Russia)
Crystallogr. Rep., 51(Suppl. 1) (2006) pp. 183-191.
This paper reports on the results of EXAFS investigations (Fe K and Ge K absorption edges) of binary supersaturated nanocrystalline solid solutions Fe100–xGex (x = 15–40 at % Ge) prepared by mechanical alloying. The nanocrystalline disordered structure of the single-phase alloys is characterized using X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. The EXAFS spectra are analyzed by solving the inverse binary problem with the use of combined data on the Fe K and Ge K absorption edges. The parameters of the partial pair correlation functions obtained indicate that the crystal lattice is characterized by strong local static distortions and short-range chemical order increasing with an increase in the germanium content. Moreover, the formation of a hexagonal-type macrostructure in the body-centered cubic (bcc) lattice occurs through a “local” stage.
EXAFS, X-RAY DIFFRACTION AND RAMAN STUDIES OF (Pb1-xLax)(Zr0.65Ti0.35)O3 (x=0.04
AND 0.09) CERAMICS IRRADIATED BY HIGH-CURRENT PULSED ELECTRON BEAM
V.V. Efimov*, E.A. Efimova*, K. Iakoubovskii**, S. Khasanov***, D.I. Kochubey, V.V. Kriventsov, A. Kuzmin****, B.N. Mavrin*****, M. Sakharov***, V. Sikolenko******, A.N. Shmakov, S.I. Tiutiunnikov*
(*Joint Institute for Nuclear Research, Dubna, Russia; **Katholieke Universiteit Leuven, Leuven, Belgium; ***Institute of Solid State Physics, Chernogolovka, Russia; ****Institute of Solid State Physics, Riga, Latvia; *****Institute of Spectroscopy, Troitsk, Russia; ******Hahn-Meitner-Institut, Berlin, Germany)
J. Phys. Chem. Solids, 67(9-10) (2006) pp. 2007-2012.
The effect of pulsed electron beam irradiation on the long-range and short-range atomic structure, as well as on the Raman phonon modes, of perovskite (Pb1-xLax)(Zr0.65Ti0.35)O3, x=0.04 and 0.09 (PLZT 4/65/35 and 9/65/35) ferroelectric ceramics is reported. X-ray powder diffraction (XRD) spectra from the single-pulse-irradiated PLZT 9/65/35 samples reveal transformation of the cubic Pm3m (Z=1) into the orthorhombic Pmmm (Z=1) structure. This symmetry change is however not observed for 10-pulse irradiation performed under the same conditions: here only an increase in the coherent scattering regions, lattice volume, and the Zr–O distance distribution is observed, as revealed by XRD and X-ray absorption spectroscopy at Zr K-edge. Raman scattering from PLZT 9/65/35 ceramics is in agreement with the symmetry reduction after single- pulse irradiation and reveals significant Raman signal intensity decrease after multiple-pulse irradiation. On the contrary, no significant structural changes could be detected in PLZT 4/65/35 ceramics after single- or multiple-pulse irradiation. Possible mechanisms of pulsed electron irradiation effects in PLZT 4/65/35 and 9/65/35 ceramics are discussed.
FIRST EXPERIMENTAL AND SIMULATION STUDY ON THE SECONDARY ELECTRON AND PHOTOELECTRON YIELD OF NEG MATERIALS (Ti–Zr–V) COATING UNDER INTENSE PHOTON IRRADIATION
Y. Suetsugu*, K. Kanazawa*, K. Shibata*, H. Hisamatsu*, K. Oide*, F. Takasaki*, R.V. Dostovalov**, A.A. Krasnov**, K.V. Zolotarev**, E.S. Konstantinov**, V.A. Chernov**, A.E. Bondar**, A.N. Shmakov
(*High Energy Accelerator Research Organization (KEK), Ibaraki, Japan;**Budker Institute of Nuclear Physics, Novosibrisk, Russia)
Nucl. Instrum. Methods Phys. Res., Sect. A, 554 (2005) pp. 92-113.
A beam duct coated with NEG materials (Ti, Zr, V), which had been known to have a low secondary electron yield (SEY), was studied for the first time under intense photon irradiation using a positron beam at the KEK B-Factory (KEKB) to investigate a way to suppress the electron cloud instability (ECI). A 2.56 m test copper chamber was coated with the NEG materials (it is called NEG coating here) by magnetron sputtering. It was installed at an arc section of the KEKB positron ring, where the chamber was irradiated by direct photons with a line density of 6.5x1014 photons m-1 s-1 mA-1. The vacuum pressure around the test chamber during a usual beam operation was lower than the case of non-coated copper chambers by a factor of 4–5. The number of electrons around positron bunches was measured by a special electron monitor up to a stored beam current of 1600 mA. The measured electron current, however, was almost the same as a non-coated copper chamber, especially at low-beam currents, and the effect of the NEG coating was smaller than expected. A simulation explained the result that abundant photoelectrons in the positron ring reduce the effect of the low SEY. The maximum SEYs of the NEG coating and non- coated copper were evaluated using a simulation as about 0.9–1.0 and 1.1–1.3, respectively, which were consistent with the values after a sufficient electron bombardment. Their photoelectron yields were also estimated as 0.22–0.28 and 0.26–0.34, respectively, and were in good agreement with the previous experimental results. The study indicates that the suppression of photoelectrons, by a beam duct with an antechamber, for example, is indispensable to make effective use of a surface with a low SEY, such as the NEG coating.
EFFECT OF HIGH-CURRENT PULSED ELECTRON BEAM IRRADIATION ON THE STRUCTURE OF La0.7Sr0.3CoO3 POWDER
V.V. Efimov*, E.A. Efimova*, K. Iakoubovskii**, D.V. Karpinskii***, S. Khasanov****, D.I. Kochubey, V.V. Kriventsov, A. Kuzmin*****, A.P. Sazonov***, V. Sikolenko******, M. Sakharov****, A.N. Shmakov, S.I. Tiutiunnikov*
(*Joint Institute for Nuclear Research, Dubna, Russia; **Katholieke Universiteit Leuven, Leuven, Belgium; ***Institute of Solid State and Semiconductor Physics, Minsk, Belarus; ****Institute of Solid State Physics, Chernogolovka, Russia; *****Institute of Solid State Physics, Riga, Latvia; ******Hahn-Meitner-Institut, Berlin, Germany)
J. Phys. Chem. Solids, 67(9-10) (2006) pp. 2001-2006.
The effect of pulsed electron irradiation on the long- and short-range order in the La0.7Sr0.3CoO3 ceramics is reported. Neutron and X-ray powder diffraction reveal that the unit cell symmetry and single-phase state of single and multiple irradiated La0.7Sr0.3CoO3 are preserved, while the oxygen atoms coordination changes towards the La0.5Sr0.5CoO3 structure. X-ray absorption data confirm this observation and further reveal the details of the shift and splitting of the Co3+ t2g and eg atomic orbitals. Possible mechanisms of pulsed electron irradiation effect in La0.7Sr0.3CoO3 are discussed.
PHASE SEPARATION IN La1-xSrxCoO3 SOLID SOLUTIONS WITH A PEROVSKITE STRUCTURE
V.V. Sikolenko*,**, A.P. Sazonov***,****, V.V. Efimov**, E.A. Efimova**, V.V. Kriventsov, D.I. Kochubey, U. Zimmermann*****
(*Hahn Meitner Institut, Berlin, Germany; **Joint Institute for Nuclear Research, Dubna, Russia; ***Institute of Solid-State and Semiconductor Physics, Minsk, Belarus; ****Institut für Kristallographie, Technische Hochschule Aachen, Aachen, Germany; *****Paul Scherrer Institute, Villigen, Switzerland)
Crystallogr. Rep., 51(Suppl. 1) (2006) рp. 67-75.
The properties of La1–xSrxCoO3 (x = 0, 0.15, 0.20, 0.30) solid solutions are investigated using neutron diffraction, positive-muon spin relaxation (precession) measurements, and extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectroscopy. The results obtained are interpreted within the model of phase separation into ferromagnetic regions enriched with Sr2+ ions and nonmagnetic regions similar in composition to the LaCoO3 compound.
STRUCTURE OF ZIRCONIUM BUTOXIDE COMPLEXES IN N-BUTANOL SOLUTIONS
V.V. Kanazhevskii, V.P. Shmachkova, N.S. Kotsarenko, V.N. Kolomiichuk, D.I. Kochubey
J. Struct. Chem., 47(3) (2006) pp. 453-457.
EXAFS and SAXS were used for structure elucidation of zirconium butoxide complexes in n-butanol at concentrations from 0.3 g to 0.015 g ZrO2 in 1 ml. The basic structural unit of the complex is a tetramer. It has two equal sides with zirconium atoms linked by double oxygen bridges and with zirconium- zirconium distances of 3.5 Ǻ. The other sides in the tetramer are 3.3 Ǻ and 3.9 Ǻ. This difference in bond lengths is explained by the different numbers of double or single ligand bridges between zirconium atoms. The tetramers are apt to undergo oligomerization to form particles with a diameter of 80 Ǻ in solution.
CHANGES IN THE ZIRCONIUM LOCAL SURROUNDING ON LIGAND SUBSTITUTION IN SOLUTIONS
V.V. Kanazhevskii, V.P. Shmachkova, N.S. Kotsarenko, V.N. Kolomiichuk, D.I. Kochubey
J. Struct. Chem., 47(5) (2006) pp. 860-868.
EXAFS and SAXS methods have been used to examine zirconium hydroxide and oxychloride aqueous solutions in the presence of sulfuric acid in a wide range of concentrations, as well as a zirconium sulfate aqueous solution. The structure of the complexes and their transformation regularities were determined. Structures of the given complexes and structures of zirconium hydroxide and zirconium oxychloride and hydroxide complexes in aqueous solutions were compared. Complexes in zirconium hydroxide and oxychloride aqueous solutions have identical structures in the presence of sulfuric acid. When the concentration ratio of sulfuric acid and the initial compound is low (20–30), the complex is an open trimer with zirconium atoms bonded by sulfate groups. Bridge sulfate groups form Zr-O-S-O-Zr bonds. Apart from the bridge sulfate groups, there are three terminal sulfate groups and three terminal hydroxyl groups for each zirconium atom. When the concentration of sulfuric acid is increased (up to a ratio of 40–100), closed trimers are observed in the solution.
CHANGE IN THE COORDINATION MODE OF NITROSYL GROUPS: TRANSFORMATION OF Pd4(μ-NO)4( μ-OCOCF3)4 INTO Pd3(NO)2(μ-OCOCF3)4(C6H5Me)2
M.V. Dayneko*, T.A. Stromnova**, L.S. Alekseev**, R.S. Shamsiev*, A.P. Belov*, D.I. Kochubey, B.N. Novgorodov
(*Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow, Russia; **Kurnakov Institute of General and Inorganic Chemistry, Moscow, Russia)
Russ. J. Inorg. Chem., 50(3) (2005) pp. 365-371.
The reaction of the tetranuclear complex of composition Pd4(CO)4(CF3COO)4 (I) with nitrogen monoxide (NO) was studied. The reaction involves the replacement of all the coordinated carbonyl groups with nitrosyl groups accompanied by redox transformations to give the tetranuclear complex Pd4(NO)4(CF3COO)4 (II). Complex II is structurally similar to the starting complex I, which was confirmed by elemental analysis, IR spectroscopy, and EXAFS. Complex II is unstable in aromatic solvents (benzene and toluene) and decomposes to form the trinuclear complex Pd3(NO)2(CF3COO)4(TolH)2 (III) and metallic palladium. X-ray diffraction analysis showed that the metal atoms in complex III form a linear chain in which each terminal atom is linked to the central atom via two bridging trifluoroacetate groups. The nitrosyl ligands are coordinated to the terminal palladium atoms in a bent end-on fashion. The scheme of the transformation of tetranuclear complex II into trinuclear complex III is proposed. This scheme was confirmed by quantum-chemical calculations.
ANALYSIS OF THE NATURE OF ADSORBED LAYERS OF ATMOSPHERIC AEROSOLS
V.P. Ivanov, S.N. Trukhan, D.I. Kochubey, K.P. Kutsenogii*, V.I. Makarov*
(*Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia)
Chem. Sustain. Devel., 14(5) (2006) pp. 449-452.
Secondary Ion Mass Spectrometry technique was used for comparison testing of the nature of adsorbed compounds on the surface of continental atmospheric aerosols, taken in industrial and background regions of Novosibirsk and Yamalo-Nenetsk, and also sea atmospheric aerosols, taken in the White Sea region.
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 (Rapid Research Lett.), 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 dipole- dipole 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.
LIFTED RECONSTRUCTION AS A FEEDBACK MECHANISM IN THE OSCILLATING CO OXIDATION ON Pt NANOFACETS: MICROSCOPIC EVIDENCE
Y. Suchorski*, W. Drachsel*, V.V. Gorodetskii, V.K. Medvedev**, H. Weiss*
(*Chemisches Institut, Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany; **Department of Chemical Engineering, University of Washington, USA)
Surf. Sci., 600(8) (2006) pp. 1579-1585.
Global and local oscillations in the CO oxidation reaction have been visualized in situ on the apex of a [1 0 0]-oriented Pt field emitter tip used as a well- defined model for catalytically active, nm-sized particles by Field Emission (FEM) and Lithium Field Desorption (Li-FDM) Microscopes. For the first time experimental evidence is provided that the reconstruction feedback mechanism of the self- maintained oscillations for the [1 0 0] and [1 1 0] orientations, which is well established on macroscopic single crystals, is also valid in the heterogeneous, nm-sized system with its different crystallographic orientations which are coupled by surface diffusion.
THE USE OF O2- RADICAL ANIONS AS SPIN PROBES FOR TESTING NANOSTRUCTURED MATERIALS BASED ON ZIRCONIUM OXIDE
N.V. Mezentseva, A.F. Bedilo, A.M. Volodin, V.A. Sadykov, V.V. Lunin*
(*Moscow Lomonosov State University, Moscow, Russia)
Russ. J. Phys. Chem., 80(7) (2006) pp. 1088-1092.
The conditions of formation of O2- radical anions on the surface of zirconium oxide systems, including nanostructured pillared clays, in interaction with hydrogen peroxide and an NO + O2 mixture of gases were studied by the EPR method. The special features of the formation of these radicals depending on the phase composition, structure, and degree of hydroxylation of the surface are discussed.
FORMATION OF MIXED Fe-Mo OXO CLUSTERS IN THE GAS PHASE
V.B. Goncharov
Russ. J. Phys. Chem., 80(2) (2006) pp. 288-290.
Reactions of oxygen-containing molybdenum clusters MoxOy (x = 1-3, y = 1-9) with iron carbonyl ions Fe(CO)n+ (n = 1-3) were studied by the ion cyclotron resonance technique. The reactions were found to yield mixed Fe–Mo oxo clusters MoxOyFe+ (x = 2, 3; y = 5, 6, 8, 9).
REACTIVITY AND HYDROGEN AFFINITY OF CHARGED MOLYBDENUM OXOCLUSTERS IN THE GAS PHASE
V.B. Goncharov
Russ. J. Phys. Chem., 80(3) (2006) pp. 486-488.
The available experimental data on proton affinity were used to calculate the hydrogen affinity (HA) of oxygen-containing molybdenum clusters. As the HA increases, the direct incorporation of the ion into a C–H bond of a hydrocarbon molecule gives way to the direct abstraction of the hydrogen atom accompanied by charge transfer to the organic fragment.
STRUCTURAL FEATURES OF MAGNESIUM OXIDES DERIVED FROM VARIOUS PRECURSORS
L.M. Plyasova, N.A. Vasilieva, I.Yu. Molina, G.V. Odegova
Russ. J. Inorg. Chem., 50(8) (2005) pp. 1131-1135.
A comparative study of the structural features of magnesium oxides derived from various precursors was carried out. The compositions and structures of the starting compounds were found to substantially influence the character and degree of modification of MgO microcrystals. Magnesium oxide, which was prepared by thermal decomposition starting from MgCO3 as a precursor, has standard unit-cell parameters. Thermal decomposition of Mg(OH)2∙ MgCO3∙2H2O yielded a highly dispersed two-phase system with different degrees of modification of the oxide. Hydration of magnesium oxide in an MgAc2 solution afforded imperfect MgO as an individual compound (a substitution solution), which has high thermal stability and activity in catalytic reactions.
DETECTION OF HYDROGEN-COPPER CLUSTERING IN Zn1-xCuxO COMPOUNDS USING NEUTRON SCATTERING METHODS
V.A. Trunov*, A.E. Sokolov*, V.T. Lebedev*, O.P. Smirnov*, A.I. Kurbakov*, J. Van den Heuvel**, E. Batyrev**, T.M. Yurieva, L.M. Plyasova, G. Török***
(*St. Petersburg Nuclear Physics Institute, Gatchina, Russia; **University of Amsterdam, Amsterdam, The Netherlands; ***Research Institute for Solid State Physics and Optics, Budapest, Hungary)
Phys. Solid. State, 48(7) (2006) pp. 1291-1297.
The atomic and cluster structure of hydrogen- treated Cu/ZnO (the major component of methanol synthesis catalysts) was studied using Bragg powder and small-angle neutron diffraction. Isotopic substitution of Cu and H was used to obtain reliable results indicating Cu and H clustering. The clusters form on the boundaries of ZnO particles and have a complex structure: a copper cluster surrounded by an adsorbed hydrogen shell has a hydrogen core. It can be assumed that this cluster configuration has a strong effect on the catalytic activity of these compounds.
PECULIARITIES OF THE ELECTRONIC SPECTRA OF MODEL Cu-Zn CATALYSTS OF METHANOL SYNTHESIS IN THE OXIDIZED AND REDUCED STATES
A.A. Khassin, S.F. Ruzankin, V.F. Anufrienko, A.A. Altynnikov, T.V. Larina, J. van den Heuvel*, T.M. Yurieva, V.N. Parmon
(*University of Amsterdam, Amsterdam, The Netherlands)
Doklady Phys. Chem., 409(2) (2006) pp. 193-197.
The anion-modified oxide Cu0.08Zn0.92O was studied to reveal the uniform light absorption over the whole visible and UV ranges. The observed phenomenon is accounted for by shifting the edge of background absorption by the high-defect structure of zinc oxide due to the appearance of impurity levels in the ZnO band gap. The oxide reduction in hydrogen at above 210°C gives rise to an absorption band at 14500–16700 cm-1 which can relate to resonance absorption of electromagnetic energy (RAEE) by copper metal nanoparticles. The observed difference of the absorption maximum from the known RAEE of copper nanoparticles (17800 cm-1) is due to decoration of the copper metal nanoparticles with zinc oxide to change dielectric permeability in the surroundings of the metal nanoparticles.
INTERACTION BETWEEN 193-nm PULSED LASER RADIATION AND α-ALUMINA
V.O. Stoyanovsky, V.N. Snytnikov, N.A. Rudina, V.N. Parmon
Techn. Phys., 51(4) (2006) pp. 514-518.
The threshold power density of 15-ns laser pulses with a wavelength 193 nm is determined for basic modes of interaction between the radiation and α-alumina. As power density Q on the target varying in the range 0.001–100 MW/cm2 increases, first the interaction mechanism changes from single-photon interaction to two-photon interaction at Q ≈ 0.1 MW/cm2. At Q ≈ 5 MW/cm2, the material sublimates and then the sublimation products ionize at Q ≈ 15 MW/cm2. At Q ≈ 100 MW/cm2, the material is removed from the surface at a rate of ≈ 10 nm per pulse.
MECHANISMS OF OXYGEN ADSORPTION AND DESORPTION ON POLYCRYSTALLINE PALLADIUM
A.N. Salanov, A.I. Titkov, V.N. Bibin
Kinet. Catal., 47(3) (2006) pp. 430-436.
The adsorption and desorption of oxygen on a polycrystalline palladium (Pd(poly)) surface (10- to 100-μm crystallites; ~32% (100), ~18% (111), ~34% (311), and ~15% (331)) at PO2≤1.3 10 5 Pa and T = 500–1300 K have been studied by TPD and mathematical modeling. The kinetics of O2 adsorption and desorption on Pd(poly) are primarily governed by the formation and decomposition of oxygen adsorption structures on the (100) and (111) crystallite faces. The O2 adsorption rate is constant at θ ≤ 0.15-0.25 owing to the formation of the p(2 x 2) structure with an Oads–surface bonding energy of D(Pd-O) = 364 kJ/mol on the (100) and (111) faces. The adsorption rate decreases with increasing coverage at θ ≤ 0.15-0.25 because of the growth, on the (100) face, of the c(2 x 2) structure, in which D(Pd-O) is reduced to 324 kJ/mol by lateral interactions in the adsorption layer. A high- temperature (~800 K) O2 desorption peak is observed for θ ≤ 0.25, which is due to O2 desorption from a disordered adsorption layer according to a second-order rate law with an activation energy of Edes = 230 kJ/mol. A lower temperature (~700 K) O2 desorption peak is observed for θ ≤ 0.25, which is due to O2 released by the c(2 x 2) structure according to a first-order rate law with Edes = 150 kJ/mol. At θ ≤ 0.25, there are repulsive interactions between Oads atoms on Pd(poly) (Caa = 5–10 kJ/mol).
STATE OF DISPERSE ALLOY PARTICLES CATALYZING HYDROCARBON DECOMPOSITION BY THE CARBIDE CYCLE MECHANISM: TEM AND EDX STUDIES OF THE Cu-Ni/Al2O3 AND Cu-Co/Al2O3 CATALYSTS
V.I. Zaikovskii, V.V. Chesnokov, R.A. Buyanov
Kinet. Catal., 47(4) (2006) pp. 603-609.
The state of disperse bimetallic alloy particles in the Cu-Ni/Al2O3 and Cu-Co/Al2O3 catalysts during their carbonization in butadiene-1,3 is studied by high- resolution electron microscopy and energy-dispersive X-ray analysis. During the formation of carbon nanofilaments by the carbide cycle mechanism, the catalyst is in a dissipative state such that the bimetallic particles vary in composition and have an anomalous component distribution in their bulk. The extrapolation of this state provides insight into the processes occurring in the dissipative system.
MANGANESE FERRITE NANOPARTICLES IN BORATE GLASS AND THEIR INFLUENCE ON THE MAGNETO-OPTICAL PROPERTIES
I.S. Edel’man*, S.A. Stepanov**, G.T. Petrovskii**, V.I. Zaikovskii, R.D. Ivantsov*, O.S. Ivanova*, D.E. Prokof’ev*, T.V. Zarubina**, E.E. Kornilova**
(*Kirensky Institute of Physics, Krasnoyarsk, Russia; **Vavilov State Optical Institute, All-Russia Research Center, St. Petersburg, Russia)
Glass Phys. Chem., 31(2) (2005) pp. 177-186.
Nanoparticles that are formed in the course of additional heat treatment in borate glasses containing iron and manganese oxide additives at low concentrations are directly observed for the first time using electron microscopy. The size, the shape, and the structure of nanoparticles and their volume distribution in the glass matrix are determined. Correlations between the nanoparticle parameters and the magnetic and magneto-optical properties of the glasses containing these particles are revealed.
GAS CHROMATOGRAPHIC ANALYSIS OF GAS EMISSIONS CONTAINING IMPURITIES OF HYDROCYANIC ACID AND CARBON OXYSULFIDE
V.I. Zheivot, S.I. Afanasieva, A.V. Simakov
J. Analyt. Chem., 61(3) (2006) pp. 253-258. Gas chromatography was used for studying the retention of HCN, COS, H2S, H2O, CO2, CO, and H2 on organic porous polymer sorbents Chromosorb-104 and Hayesep C either unmodified or modified with different amounts of H3PO4. The effect of water on the signal of the thermionic detector was studied, and the conditions of the determination of 6–23 ppm HCN in aqueous solutions were found: column (3 m 2 mm) with Hayesep C containing 15 wt % H3PO4. A procedure was developed for the determination of 15-1000 ppm COS in the presence of high concentrations (up to 1 vol %) of H2S on a column (3 m 2 mm) packed with Chromosorb-104 modified with 0.5 wt % H3PO4 with a flame photometric detector (396 nm). A basic scheme was proposed for the gas chromatographic analysis of the products of the catalytic detoxication of gas emissions in the process of coal gasification.
SPECIFIC FEATURES OF THE GAS-CHROMATOGRAPHIC DETERMINATION OF THE REACTION PRODUCTS IN THE CATALYTIC DECOMPOSITION OF HYDROGEN SULFIDE
V.I. Zheivot, V.N. Krivoruchko, A.S. Medvedev*, O.V. Voroshina*
(*Institute of Semiconductor Physics, Novosibirsk, Russia)
J. Analyt. Chem., 61(4) (2006) pp. 334-337.
Specific features of the determination of hydrogen sulfide in the presence of hydrogen were studied by gas chromatography with the use of a thermal conductivity detector and argon as the carrier gas. A chromatographic column with HayeSep A modified with 10 wt % H3PO4 was proposed for the simultaneous determination of both components. It was demonstrated that the elution curve of hydrogen sulfide in an argon atmosphere has a non-Gaussian shape because of the interaction of hydrogen sulfide with the tungsten filament of the sensing element of the catarometer. To eliminate this interaction, it was recommended that a gold-plated tungsten filament be used in the detector.
GAS CHROMATOGRAPHY ON CARBON ADSORBENTS: CHARACTERIZATION, SYSTEMATIZATION, AND PRACTICAL APPLICATIONS TO CATALYTIC STUDIES
V.I. Zheivot
J. Analyt. Chem., 61(9) (2006) pp. 832-852.
The results of the characterization of graphite-like carbon materials by X-ray diffraction, electron microscopy, and adsorption and gas chromatography are discussed. All carbon-containing adsorbents are systematized in accordance with their structure and adsorption characteristics, chemical nature, and chromatographic surface properties. The adsorption and gas-chromatographic properties of carbons and other adsorbents are compared. The purposeful regulation of the chemical nature of carbon adsorbent surfaces is considered; it significantly extended the gas-chromatographic capabilities of carbon-containing materials, in particular, in studies of the product composition of catalytic reactions.
DISSOLUTION KINETICS OF CsHSO4 AND CsHSO4/SiO2 COMPOSITES IN AQUEOUS SOLUTIONS
V.G. Ponomareva*, G.V. Lavrova*, V.V. Malakhov, L.S. Dovlitova
(*Institute of Solid- State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Inorg. Mater., 42(10) (2006) pp. 1115-1120.
Using a differential dissolution method, the dissolution kinetics of CsHSO4 and CsHSO4/SiO2 composites (40, 60, and 70 mol % SiO2) in aqueous solutions have been studied. The results demonstrate that the composites and bulk CsHSO4 differ markedly in dissolution rate. In addition, the dissolution rate depends on the composition of the composite and decreases significantly as the SiO2 content is raised from 0 to 70 mol %, even though the particle size of the salt is notably smaller in the composites. The composites of the same composition may contain cesium hydrogen sulfate in several states, differing in dissolution rate.
TEXTILES FROM FROZEN TOMBS OF IV–III CENTURIES B.C. IN THE ALTAI MOUNTAINS
N.V. Polosmak*, L.P. Kundo**, G.G. Balakina**, V.I. Mamatyuk**, V.G. Vasiliev**, E.V. Karpova**, V.V. Malakhov, A.A. Vlasov, I.L. Kraevskaya, L.S. Dovlitova, E.A. Korolyuk**, E.G. Tsareva***
(*Institute of Archaeology and Ethnography, Novosibirsk, Russia; **Vorozhtzov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia; ***Museum of Anthropology and Ethnography, St. Petersburg, Russia)
Novosibirsk, Publishing House SB RAS, 2006, 265 pp.
Results of studying inorganic components of ancient textile samples are reported. Inductively coupled plasma–atomic emission spectrometry (ICP-AES) and X-ray fluorescent spectroscopy (XRFS) techniques were used to determine the textile elemental composition. In general, more than 100 fragments of ancient textiles were characterized. A new reference-free high-sensitive method of differential dissolution (DD) was used for the first time for identification and quantitative determination of the phase (mineral) composition of inorganic constituents of the ancient textiles.
PHYSICOCHEMICAL STUDIES OF CERAMICS (WITH WARES OF THE TRANSITION PERIOD FROM BRONZE TO THE IRON AGE AS AN EXAMPLE)
V.A. Drebuschak*, L.N. Mylnikova**, T.N. Drebuschak***, V.V. Boldyrev***, V.I. Molodin**, E.I. Derevyanko**, V.P. Mylnikov**, A.V. Nartova
(*Institute of Mineralogy and Petrography, Novosibirsk, Russia; **Institute of Archaeology and Ethnography, Novosibirsk, Russia; ***Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Eds. V.V. Boldyrev, V.I. Molodin, Novosibirsk, Publishing House SB RAS, 2006, 98 pp.
An economically and informatively optimal set of analytic physicochemical tools was chosen for studying specimens of ancient ceramics. The authors found it most appropriate to combine thermogravimetric (TG), powder X-ray diffraction (XRD) and petrographic techniques. TG and XRD are most effective for characterization of clay minerals including their thermal treatment products and of well crystalline nonplastic minerals, while petrography provides quantitative data on the ratio of clay components and nonplastic debris. Algorithms of analytic procedures were developed for each of these methods.
COPPER-PROMOTED COBALT CATALYSTS FOR 2,3-DIHYDROFURAN SYNTHESIS
L. Leite*, V. Stonkus*, K. Edolfa*, L. Ilieva**, L.M. Plyasova, V.I. Zaikovskii
(*Latvian Institute of Organic Synthesis, Riga, Latvia; **Institute of Catalysis, Bulgarian Academy of Sciences, Sofija, Bulgaria)
Appl. Catal., A, 311 (2006) pp. 86-93.
The conversion of 1,4-butanediol to 2,3-dihydrofuran in the liquid phase has been studied over novel kaolin-supported Co–Cu catalysts, prepared by means of a simple mechanochemical method. The improvement of the catalytic properties and decrease in the optimum reduction temperature of Co–kaolin catalysts, promoted by copper, has been observed. It was established that a Co:Cu ratio 5:1 is optimum for the specific activity and for the yield in the conversion of 1,4-butanediol to 2,3-dihydrofuran. In the present study, the highest 2,3-dihydrofuran yield (81%) was obtained with the ultrasonically treated catalyst and after reduction pretreatment at 320–350°C. The existence of an optimum reduction temperature for the catalyst pretreatment was established. In agreement with the results, obtained in previous studies, the high 2,3-dihydrofuran yield is favoured by the coexistance of cobalt both in the metallic and oxidic state. The increased specific activity of copper-containing catalysts could be related to the lowering of the reduction temperature, which leads to a hexagonal metallic cobalt phase formation. The latter is favourable for 2,3-dihydrofuran synthesis. The advantage of mechanochemical preparation of Co–Cu (5:1) catalyst is that the method prevents penetrating of cobalt ions into the support, thus the whole amount of cobalt loaded is available for the catalyst performance. This is one of the probable reasons for higher specific activity of the 2,3-DHF formation over these catalysts.
CATALYST FOR DEHYDROGENATION OF LOWER С3-С5 PARAFFINS IN FIXED BED OVER NOVEL ALUMINA CERAMOMETAL SUPPORT
N.A. Pakhomov, S.F. Tikhov, Yu.N. Bespalko, V.S. Babenko, A.I. Titkov, A.N. Salanov, V.A. Sadykov, R.A. Buyanov
Crit. Technol. Membranes, 29(1) (2006) pp 38-42.
The effect of a ratio of powder metallic aluminum and the product of thermochemical activation gibbsite in the initial charge on the textural and strength properties of the ceramic-metal Al2O3-Al catalysts has been studied. The optimal composition of the initial charge, providing preparation of a support with the best texture-mechanical properties, was determined. The chromium oxide catalyst supported on a new ceramic-metal support cermet exhibits in the reaction of lower C3-C4 paraffin dehydrogenation the activity and selectivity which comply with the best world analogs.
THE HEAT OF WETTING OF ALUMINUM HYDROXYOXIDE OBTAINED BY THE THERMAL ACTIVATION OF HYDRARGILLITE
>Yu.D. Pankratiev, Yu.Yu. Tanashev, E.V. Kulko, A.S. Ivanova, E.M. Moroz, V.N. Parmon
Russ. J. Phys. Chem., 80(7) (2006) pp. 1037-1043.
Changes in the volume and surface properties of thermally activated hydrargillite, so-called centrifugal thermal activation (CTA) product (empirical formula Al2O3 0.85H2O), during its calcining in air with gradually increasing temperature from 90 to 1100°C were studied. At each stage of calcining, weight loss, phase composition, texture characteristics, and the heat of wetting with water at 25°C were determined. Measurements of the heat of wetting showed that the energy and, therefore, chemical state of the surface changed during thermal treatment. The data obtained were used to calculate the heats of adsorption qads of water vapor by CTA samples with different water contents; the range of qads variations was 50-250 kJ/mol. The values obtained are compared with literature data.
ACID-BASE PROPERTIES OF ALUMINA PREPARED FROM A HYDRATED PRODUCT OF CENTRIFUGAL THERMAL ACTIVATION OF HYDRARGILLITE (CTA-PRODUCT)
E.V. Kulko, A.S. Ivanova, A.A. Budneva, E.A. Paukshtis
React. Kinet. Catal. Lett., 88(2) (2006) pp. 381-390.
Acid-base properties of aluminas prepared by thermal treatment of a hydrated CTA-product at 600°C were studied. The CTA-oxides, representing γ-Al2O3, were shown to contain terminal and bridged OH-groups. The concentration of the terminal OH-groups in the CTA-oxides was found to exceed their concentration in γ-Al2O3 prepared by dehydration of the “precipitated” pseudoboehmite, whereas the concentration of the bridged OH-groups in the CTA-oxides was lower than that in γ-Al2O3 prepared from pseudoboehmite. The total concentration of the surface Lewis acid sites in CTA- oxides varies within the limits of 2.80–4.14 μmol/m2 and is essentially above that in γ-Al2O3 (2.25 μmol/m2). The distinctive feature of the CTA-oxides is that their surface contains strong Lewis acid sites with γCO = 2220 and 2238 cm–1. The total concentration of basic sites in the CTA oxides is lower than that in γ-Al2O3, however, in contrast to γ-Al2O3, they contain strong basic sites with γCDCl3 = 2200 cm-1.
PREPARATION FACTORS INFLUENCING THE EFFECTIVENESS OF SAPO CATALYSTS IN N-PARAFFINS HYDROISOMERIZATION
Stud. Surf. Sci. Catal., 162 (2006) pp. 897-904.
The present work deals with a comparison of synthesis procedures of silicoaluminophosphates of AEL and ATO structural types starting with the same Al, P and Si sources but differing in template origin. On the base of performed experiments on preparation of these materials by means of hydrothermal synthesis of initial silicoaluminophosphate gel general factors which determine a quality of final product have been specified. It is shown that within both crystalline systems a treatment of starting reaction mixture with a wide range of Si/Al ratios is possible to result in high crystalline goal material with no admixture of impurity phases. It is found that AEL phase allows much broader variations in its preparation conditions comparatively with ATO phase synthesis. The next parameters are determined to have more expressed importance for preparation of good quality SAPO-31 samples: order of reagent mixing, intensity and duration of stirring, pH control for each stage of preparation. Disturbance of the reaction boundary conditions leads to incomplete crystallization of initial gel or else to appearance of competing phase. Both cases may be a matter for insufficient quality of goal hydroisomerization catalyst in respect to its activity and selectivity. In the present work influence of parameters of preparation of SAPO-11 and SAPO-31 materials is demonstrated in terms of their catalytic performance in hydroconversion of n-octane. The effect of pore structure differences between AEL and ATO on group distribution of C8 isomers as well as on isomer distribution within methylheptanes and dimethylhexanes is shown for high quality samples. Taking into account obtained experimental data a conclusion is made on possibility of use of substituted aluminophosphate with ATO structure with regard to hydroisomerization of long-chain paraffin molecules. Catalytic properties of these materials are totally determined by a possibility of synthesis of high crystalline pure ATO phase with high degree of substitution of Al and P atoms of crystalline lattice with isomorphous element.
NANOSTRUCTURED V2O5/TiO2 (ANATASE) CATALYSTS: SYNTHESIS, CHARACTERIZATION, CATALYTIC PROPERTIES
G.A. Zenkovets, G.N. Kryukova, S.V. Tsybulya, V.Yu. Gavrilov
In “New Challenges in Catalysts 4”, Eds. P. Putanov, Belgrade, The Serbian Academy of Science and Arts, Branch in Novi Sad., 2005, pp. 239-254.
This paper describes a synthesis of the nanostructured vanadia-based catalysts possessing interfacial boundaries between V2O5 and TiO2 (anatase) particles. The process of structural formation of the interface at the different stages of the synthesis of catalysts with V2O5 loading lying between 5 and 50 % wt has been studied. XRD, TEM, ESR, 51V NMR and Raman spectroscopes provide detailed characterization of the materials, particularly, the atomic arrangement of the interface and state of oxidation the vanadium ions. Data on the determination of catalysts texture in a wide temperature region are given. These catalysts appear to be effective for some selective oxidation reactions.
THE STATE OF THE ART AND PROSPECTS FOR DEVELOPMENT IN THE FIELD OF SUPPORTED PALLADIUM CATALYSTS
A.S. Lisitsyn, V.N. Parmon, V.K. Duplyakin*, V.A. Likholobov* (*Institute of Hydrocarbons Processing, Omsk, Russia)
Russ. Chem. J., 50(4) (2006) pp. 140-153.
The present-day status of researches in the field of supported catalysts with metallic palladium as the active phase is briefly reviewed. Most attention is given to peculiarities of catalyst synthesis from different metal precursors on oxide and carbon supports, to interaction of the active phase with the support, and to comparison of Pd and Pt catalysts. Multiplicity of the factors acting during the catalyst genesis, and a close and intricate relationship between these factors have been pointed out. The nature of the metal precursor, texture and functional coverage of the support, as well as various treatments prove capable of affecting strongly the catalytic properties but none of the factors can be considered principal one, and any can play both positive and negative role, depending on other conditions. Possibilities for further improving and new ways for industrial application of Pd catalysts are also noted.
EFFECTS OF CARBON SURFACE OXIDES ON THE DISPERSION OF Pt/C CATALYSTS PREPARED VIA ADSORPTION OF HEXACHLOROPLATINIC ACID: A NEW INSIGHT
A.N. Kholodovich, P.A. Simonov
React. Kinet. Catal. Lett., 89(1) (2006) pp. 167-175.
A new concept is advanced to explain some effects of oxygen-containing groups of the carbon surfaces on the dispersion of Pt/C catalysts prepared through the adsorption of H2PtCl6 onto porous carbon powders followed by the reduction with H2. These groups alter the electrochemical properties of the support and, therefore, influence the nature and amount of the adsorbed catalyst precursors formed during a redox reaction between the carbon surface and H2PtCl6, that reflects on the dispersion of Pt/C. A way to account for their impact on platinum dispersion is offered. It allows revising and uniting many literature data related to this problem.
INVESTIGATIONS OF THE ACTIVATION OF ALUMINIUM METAL AS THE INITIAL STAGE OF PREPARATION OF ALUMINA-BASED CATALYSTS AND SUPPORTS
M.V. Trenikhin*, V.K. Duplyakin, A.I. Nizovskii, A.G. Kozlov**
(*Institute of Hydrocarbons Processing, Omsk, Russia; **Omsk Department of the Institute of Semiconductor Physics, Omsk, Russia)
Chem. Sustain. Devel., 14(1) (2006) pp. 63-71. The initial stage of synthesis of ‘metal of alumina’ catalysts is studied. The proposed procedure allows the amount of harmful waste to be decreased considerably. The method is based on the direct interaction of pre-treated aluminium metal and water. It is shown that diffusion phenomena underlie the process of aluminium activation with a fluid In-Ga metal fusion. A method is proposed for estimation of the coefficient of gallium bulk diffusion into grains of polycrystalline aluminium.
CHEMICAL INTERACTION OF THE In-Ga EUTECTIC WITH Al AND Al-BASE ALLOYS
M.V. Trenikhin*, A.V. Bubnov*, A.I. Nizovskii, V.K. Duplyakin*
(*Institute of Hydrocarbons Processing, Omsk, Russia)
Inorg. Mater., 42(3) (2006) pp. 256-260.
The chemical interaction of the indium–gallium eutectic with Al and Al-base alloys is studied by X-ray diffraction, optical microscopy, and electron microscopy. Experimental data are presented that shed light on the reaction mechanism and the diffusion processes responsible for the subsequent disintegration of the material and its dissolution in water. Mechanical tests show that the activation of aluminum leads to a transition from plastic to brittle fracture.
HIGH-TEMPERATURE CATALYSTS WITH A SYNERGETIC EFFECT OF PD AND MANGANESE OXIDES
S.A. Yashnik, Z.R. Ismagilov, V.V. Kuznetsov, V.V. Ushakov, V.A. Rogov, I.A. Ovsyannikova
Catal. Today, 117(4) (2006) pp. 525-535.
A synergetic effect in the catalytic activity has been found after palladium introduction in Mn–Al–O systems. The magnitude of the synergetic effect depends on the types of the oxidic manganese species: oxide Mn3O4, spinel (Mn, Mg)[Mn, Al]2O4 or hexaaluminate (Mn, Mg)LaAl11O19. The synergetic effect of Pd and manganese-containing compounds is observed only if palladium is introduced to the low- temperature precursor of the manganese alumina spinel or manganese hexaaluminate. The synergetic effect is not observed when high-temperature samples with formed spinel or hexaaluminate phases are modified with Pd.
CARBONIZATION AND REGENERATION OF Mo/ZSM-5 CATALYSTS FOR METHANE DEHYDROAROMATIZATION
Z.R. Ismagilov, L.T. Tsykoza, E.V. Matus, G.S. Litvak, I.Z. Ismagilov, O.B. Sukhova
Eurasian Chem.-Tech. J., 7(2) (2005) pp. 115-121.
The character of carbonaceous deposits formed during methane dehydroaromatization reaction in the presence of Mo/ZSM-5 catalyst was studied by differential thermal analysis. The dependence of the concentration and condensation degree (C/H ratio) of the carbonaceous deposits on the catalyst synthesis conditions (Mo content = 1-10%, Si/Al ratio in the initial H-ZSM-5 = 17-45) and reaction conditions (feed flow rate = 405-1620 h-1, methane concentration = 90-98%, reaction temperature = 720-780°C) was investigated. The oxidative treatment conditions of carbonized Mo/ZSM-5 catalysts providing stable operation of the catalysts under multiple reaction- oxidative treatment cycles were selected.
ON THE H-FORM OF NATROLITE
A.Yu. Likhacheva*, S.A. Veniaminov, E.A. Paukshtis, I.A. Belitsky*
(*Institute of Mineralogy and Petrology, Novosibirsk, Russia)
Eur. J. Mineral., 18(3) (2006) pp. 345-350.
To resolve the problem of existence of the H-form of natrolite, the thermal decomposition of NH4-exchanged natrolite (as a precursor of the H-form) was studied by gas chromatography, IR spectroscopy and X-ray diffraction. Throughout the decomposition, the de-ammoniation is immediately followed by dehydroxylation, which is evidence for the instability of the H-natrolite formed after the removal of NH3, and leads to a negligibly small concentration of the OH-groups. The natrolite structure can not persist after the removal of NH3. In the final step of decomposition, the adsorption of NH3 onto Lewis centres accumulated in the amorphosed framework hinders the de-ammoniation. This seems to be one of the major factors which influence the observed increase in the activation energy for NH3 desorption from 117(±13) kJ/mol in the initial step to 270(±20) kJ/mol. Smooth vacuum degassing of NH4-natrolite at 550 K leads to partial de-ammoniation, rather than formation of H-natrolite.
A HOMOCHIRAL METAL-ORGANIC MATERIAL WITH PERMANENT POROSITY, ENANTIOSELECTIVE SORPTION PROPERTIES, AND CATALYTIC ACTIVITY
D.N. Dybtsev*, A.L. Nuzhdin, H. Chun**, K.P. Bryliakov, E.P. Talsi, V.P. Fedin*, K. Kim**
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Pohang University of Science and Technology, Pohang, Gyungbuk, Republic of Korea)
Angew. Chem. Int. Ed., 45(6) (2006) pp. 916-920.
A new approach to the synthesis of homochiral metal–organic porous materials starting from readily available chemicals is described. A 3D homochiral microporous framework that has permanent porosity, size- and enantioselective guest-sorption properties, as well as remarkable catalytic activity with size and chemoselectivity, and high conversion in the oxidation of thioethers to sulfoxides was successfully produced.
SYNTHESIS OF METHYLFORMATE THROUGH CATALYTIC DEHYDROGENATION OF METHANOL OVER COPPER-CONTAINING CATALYSTS
A.A. Vedyagin, P.G. Tsyrulnikov*, T.A. Dashuk*, N.O. Struikhina*, A.V. Bubnov*, N.V. Antonicheva*
(*Institute of Hydrocarbons Processing, Omsk, Russia)
Ind. Chem., 10 (2005) pp. 492-497.
The work is devoted to optimization of the composition and preparation conditions of copper- containing catalysts for dehydrogenation of methanol into methylformate. It is shown that the effective catalysts can be prepared using copper nitrate as the active component precursor. The optimal copper loading in the catalyst is established at the level of 5%.
DETONATIVE SPUTTERING FOR DECISION OF PROBLEMS OF HYDROGEN ENERGY
V.Yu. Ulyanitskii*, A.A. Shtertser*, S.B. Zlobin*, V.I. Matrenin*, I.V. Schipanov*, S.Yu. Serykh*, A.S. Stikhin*, L.M. Tretiakova*, V.A. Sadykov, S.N. Pavlova, S.F. Tikhov, V.A. Kuzmin
(*Institute of Hydrodynamics, Novosibirsk, Russia)
Int. Sci. J. Alternative Energy Ecol., 9 (2006) pp. 137-144.
Regularities for preparation of supports and catalysts based on layered metal-oxide composites, obtained by detonative sputtering of powder oxides on metal foil, and its application for catalysis, is studied.
THE YTTRIA-STABILIZED ZIRCONIA INTERFACIAL COATINGS ON NICALON FIBER
N.I. Baklanova*, A.T. Titov*, A.I. Boronin, S.V. Koscheev
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
J. Eur. Ceramic Soc., 26(9) (2006) pp. 1725-1736.
Sols of yttria-stabilized zirconia may be used as simple, readily processable and accurate controllable precursors for the ZrO2 interfacial coatings on SiC-based NicalonTM fibers. The ZrO2 interfacial coatings of predictable crystal phase compositions were obtained in dependence of yttria dopant level. The morphology, composition and oxidation resistance of coated fibers were evaluated by SEM, EDS, XPS, XRD, and Raman analysis. All coatings obtained are uniform, continuous and adherent to substrates. The delamination within the ZrO2 interfacial coating was found. Possible reasons of this phenomenon are discussed. The peculiarities of the behavior of Y-stabilized ZrO2-coated fibers in air at elevated temperature are considered.
FORMATION OF Pt(O)/Si(Ca)O2 NANOFIBERS UPON THE REACTION OF PLATINUM AEROSOL PARTICLES WITH A CALCIUM- AND SILICON-CONTAINING MATERIAL
A.S. Ivanova, E.M. Slavinskaya, V.I. Zaikovskii, I.N. Polukhina, O.V. Chub, A.S. Noskov
Doklady Phys. Chem., 407(1) (2006) pp. 80-83.
It was found that crystalline nanofibers (up to
1000 nm high and about 50 nm in diameter) are formed on the surface of the calcium- and-silicon-containing high-temperature material upon its interaction with platinum aerosol particles at 900°C. The nascent nanofibers represented quartz containing dissolved calcium, Si(Ca)O2, the calcium concentration being higher on the top of the fibers. Platinum is also present on the top of the nanofibers, in particular, oxidized platinum occurs on the surface and metal particles (~5 nm) are located under the Si(Ca)O2 layer.
TEXTUROLOGY
V.B. Fenelonov, M.S. Melgunov
In “Surface and Nanomolecular Catalysis”, Ed. R. Richards, CRC Press, 2006, pp. 257-336.
Review of modern state-of-art in the field of texturology of catalysts and other porous materials.
IS IT POSSIBLE TO GENERALIZE THE PROBLEMS OF POROUS MATERIALS FORMATION, STUDY AND EXPLOITATION?
M.S. Melgunov, V.B. Fenelonov
In “Surface Chemistry in Biomedical and Environmental Science”, Eds. J.P. Blitz, V.M. Gun’ko, Springer, The Netherlands, 2006, pp. 69-78.
The transition from the variety of “scientific bases of preparation” of porous materials (adsorbents, catalysts, etc.) to a uniform fundamental knowledge is discussed. This transition is based on allocation of two different but general levels of porous materials science: molecular (atomic) and supramolecular (textural). Fundamental relationships and laws are discussed in the application of porous materials for catalysis and adsorbents with respect to texture and structure.
CrAl ALLOY-BASED MONOLITH WITH POLYMODAL PORE STRUCTURE FOR PARTIAL OXIDATION OF METHANE TO SYNTHESIS-GAS
S.F. Tikhov, V.V. Usoltsev, V.A. Sadykov, S.N. Pavlova, O.I. Snegurenko, L.L. Gogin, Z.Yu. Vostrikov, A.N. Salanov, S.V. Tsybulya, G.S. Litvak, G.V. Golubkova*, O.I. Lomovskii*
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Stud. Surf. Sci. Catal., 162 (2006) pp. 641-648.
The main stages of the CrAl alloy-based monoliths preparation from the Al and Cr powders through mechanical alloying, hydrothermal treatment and calcination have been described. The textural, mechanical and catalytic properties in the partial oxidation of methane on the monolithic cermets are presented.
DEFECT MAGNESIUM OXIDES CONTAINING ACETATE AND NITRATE ION FRAGMENTS INCORPORATED IN THE OXIDE STRUCTURE
N.A. Vasilieva, L.M. Plyasova, G.V. Odegova
Kinet. Catal., 47(3) (2006) pp. 437-444.
The results of studies on the synthesis of defect magnesium oxides by MgO hydration in salt solutions are summarized. The incorporation of oxygen- containing salt anions into the anionic hydroxide/oxide framework is described. In this case, the anion residue whose oxygen atoms belong to the oxygen framework of the oxide is incorporated in the octahedral oxygen cell of the oxide to occupy the place of a virtual magnesium cation. A portion of cationic vacancies remains free, whereas a portion is occupied by the transformed anion residue with a positive charge other than 2+. As a result, defect magnesium oxides are formed as substitutional solid solutions. The structure and charge heterogeneity of defect oxides is responsible for their high catalytic activity.
WO3/MO2 (M = Zr, Sn, Ti) HETEROGENEOUS ACID CATALYSTS: SYNTHESIS, STUDY, AND USE IN CUMENE HYDROPEROXIDE DECOMPOSITION
G.M. Maksimov, G.S. Litvak, A.A. Budneva, E.A. Paukshtis, A.N. Salanov, V.A. Likholobov*
(*Institute of Hydrocarbons Processing, Omsk, Russia)
Kinet. Catal., 47(4) (2006) pp. 564-571.
Thirty (5–40)% WO3 /MO2 (M = Zr, Ti, Sn), heterogeneous acidic catalysts have been synthesized by two methods, specifically, via homogeneous acid solutions and from solutions brought to pH 9 with ammonia, both followed by calcination at 600-900°C. The catalysts have been characterized by IR spectroscopy and scanning electron microscopy, and their aqueous washings have been analyzed. Their acidity has been determined by the thermal analysis of samples containing adsorbed pyridine, and in terms of the proton affinity scale. Catalytic activities have been compared for cumene hydroperoxide (CHP) decomposition at 40°C in cumene and acetone. For all M, the catalysts are one type and contain W in strongly and weakly bound states, the latter being a polyoxometalate that can be washed off. Both tungstate phases are active in acid catalysis. Brønsted acid sites with a broad strength distribution have been found. The strongest of them are heteropolyacid protons. The catalysts 30% WO3/SnO2 and 20% WO3/ZrO2 (in acetone) and 10–20% WO3/TiO2 (in cumene) are the most active in CHP decomposition, and their activity is not related to their total acidity. Phases containing W6+ that form during the high-temperature synthesis are responsible for the high acidity, and additional protons that may appear owing to W6+ reduction can play only a minor role.
NANOSCALE OXIDES AS DESTRUCTIVE SORBENTS FOR HALOGENATED HYDROCARBONS
A.M. Volodin, A.F. Bedilo, D.S. Heroux*, V.I. Zaikovskii, I.V. Mishakov, V.V. Chesnokov, K.J. Klabunde*
(*Kansas State University, Manhattan, Kansas, USA)
Surf. Chem. Biomed. Environ. Sci., NATO Science Series II: Mathematics, Physics & Chemistry, Springer-Verlag GmbH, Eds. J. Blitz, V. Gun'ko, 2006, pp. 403-412.
Destructive adsorption of halocarbons on nanocrystalline oxides has been studied. The effect of the nanoparticle size and phase composition on the reaction kinetics is discussed. The reactivity of nanocrystalline oxides has been found to increase after deposition of a permeable carbon coating. The possibility of synthesis of new nanocrystalline halogenated materials using nanoscale oxides as precursors has been demonstrated.
MESOPOROUS TITANIUM SILICATES AS CATALYSTS FOR THE LIQUID-PHASE SELECTIVE OXIDATION OF ORGANIC COMPOUNDS
O.A. Kholdeeva, N.N. Trukhan
Russ. Chem. Rev., 75(5) (2006) pp. 411-432.
The data on the synthesis, physicochemical and catalytic properties of mesoporous titanium silicate materials published to date are surveyed. The relationship between the structure of these materials and their catalytic properties in the liquid-phase selective oxidation of organic compounds with peroxides is considered. The emphasis is placed on the problems of stability of mesoporous titanium silicate catalysts and the possibility of their recycling. The bibliography includes 264 references.
RELATION BETWEEN THE SUPERMOLECULAR STRUCTURE AND OPTICAL PROPERTIES OF LIQUID CRYSTAL – PHOTOPOLYMER COMPOSITE FILMS
G.M. Zharkova*, I.V. Samsonova*, S.A. Streltsov*, V.M. Khachaturyan*, A.P. Petrov*, N.A. Rudina
(*Institute of Theoretical and Applied Mechanics, Novosibirsk, Russia)
Mol. Cryst. Liq. Cryst., 449 (2006) pp. 57-70.
Composite materials with spatially alternating polymer and nematic liquid crystal layers have been obtained. The tetraacrylate pentaerrythritol monomer, methylene blue and nematic liquid crystals were used as the pre-polymer composition. Scanning electron microscopy results show that the supermolecular structure holographically formed in the film depends on the relation between the nematic liquid crystal and dye concentrations in the pre-polymer composition and the curing energy. This system allows preparation of electrically switchable transmission gratings with first-order diffraction efficiencies up to 30–55%. The formed gratings could be switched from diffracting to transparent state at 4.5–7.5 V/µm. The turn-on and turn-off times were 200–300 µs and 1.2–3 ms, depending on the particular composition of the initial composition. Stability of grating characteristics was examined over a 1.5-year period of grating storage.
FORMATION OF NANOPARTICLES OF TiO2 AND Al2O3 AT COMBUSTION OF METAL DROPLETS
S.A. Khromova, V.V. Karasev*, A.A. Onischuk*, O.G. Glotov*, V.E. Zarko*
(*Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia)
In “Nonequilibrium Processes”, vol. 2: Plasma, Aerosols, and Atmospheric Phenomena, Eds. G. Roy, S. Frolov, A. Starik, TORUSPRESS, Moscow, 2005, pp. 225-234.
The investigations of metal droplets combustion are inspired by both fundamental interest and possible applications. In particular the combustion of metal powder can be an effective way of synthesis semiconductor and ceramic oxide nanoparticles. Aluminum powder serves as an energetic additive to the rocket propellants. In respect to this application a single metal particle burning in air at 1 atm was selected by many researches as a simple model for theoretical and experimental study. Even though in most practical propellants metal particles burn at high pressures, with CO2, CO, and H2O oxidizers, the knowledge of more simple mechanism details will give an insight to the processes occurring in the real systems. Combustion of Ti droplets results in formation of TiO2 nanoparticle predominantly in anatase crystal modification. The anatase modification is active in various photocatalytic redox reactions. That is why the combustion route of synthesis of TiO2 nanoparticles has attracted a great interest in the literature. However at present there is lack of experimental data on metal oxide nanoparticle formation which prevents elaboration of appropriate model of the metal particle combustion which can predict the characteristics of oxide nanoaerosol. In this work TiO2 and Al2O3 nanoparticle formation was studied during combustion of Ti and Al droplets in air at atmospheric pressure.
IMMOBILIZED GLUCOAMYLASE: A BIOCATALYST OF DEXTRIN HYDROLYSIS
G.A. Kovalenko, L.V. Perminova, G.V. Plaksin*, T.V. Chuenko, O.V. Komova, N.A. Rudina
(*Institute of Hydrocarbons Processing, Omsk, Russia)
Appl. Biochem. Microbiol., 42(2) (2006) pp. 145-149.
Heterogeneous biocatalysts of starch saccharification based on glucoamylase and carbon- containing carriers were obtained, and their biocatalytic properties in the enzymatic hydrolysis of corn dextrins were studied. It was shown that the morphology of the surface carbon layer of carriers markedly affected the properties of biocatalysts. Glucoamylase immobilized by adsorption on the surface of carriers covered with a layer of catalytic filamentous or pyrolytic carbon had the maximum enzymatic activity and stability, whereas biocatalysts prepared on the basis of carriers that had no carbon layer or were covered with graphite-like surface carbon had a low activity and stability.
MODIFIED CERIA-ZIRCONIA FLUORITE-LIKE CATALYSTS FOR THE COMBUSTION OF METHANE
T.G. Kuznetsova, V.A. Sadykov, L.Ch. Batuev, E.M. Moroz, E.B. Burgina, V.A. Rogov, V.V. Kriventsov, D.I. Kochubey
J. Natural Gas Chem., 15(3) (2006) pp. 149-163.
For dispersed ceria-zirconia-based solid solutions prepared via the polymerized complex method and annealed at 700°C, effects of bulk doping by Ca, Mn, Co, Bi or Nb cations and surface modification by Mn and Pt on their structural features, surface/bulk oxygen reactivity and catalytic activity in methane combustion are considered. With up to 20 mol% doping, a structural type of homogeneous solid solutions of anion-deficient fluorite with disordered anion vacancies is formed. Doping by transition metal cations or Pt increases the mobility and reactivity of the surface/bulk oxygen. A broad variation in specific rates of methane combustion for the studied systems was observed, suggesting structural sensitivity of this reaction. In general, there is no universal relationship between the oxygen mobility, the reactivity and the catalytic activity in methane combustion, which is explained by the factor of specific methane activation on surface active sites. For the Pt-promoted samples, Pt efficiency in methane activation depends on the Pt-support interaction, and the most favorable ones being mixed Pt/MnOx and Pt/NbOx clusters on the surface of the supports that exhibit high lattice oxygen mobilities.
FUEL-RICH METHANE COMBUSTION: ROLE OF THE Pt DISPERSION AND OXYGEN MOBILITY IN A FLUORITE-LIKE COMPLEX OXIDE SUPPORT
V.A. Sadykov, T.G. Kuznetsova, Yu.V. Frolova-Borchert, G.M. Alikina, A.I. Lukashevich, V.A. Rogov, V.S. Muzykantov, L.G. Pinaeva, E.M. Sadovskaya, Yu.A. Ivanova, E.A. Paukshtis, N.V. Mezentseva, L.Ch. Batuev, V.N. Parmon, S. Neophytides*, E. Kemnitz**, K. Scheurell**, C. Mirodatos***, A.C. van Veen***
(*Institute of Chemical
Engineering and High-Temperature Processes, Patras, Greece; **Institute for Chemistry, Humboldt University, Berlin, Germany; ***Institut de Recherches sur la Catalyse, Villeurbanne, France)
Catal. Today, 117(4) (2006) pp. 475-483.
For catalysts comprised of Pt supported on to 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.
PROPERTIES OF Ce–Zr–La–O NANO-SYSTEM WITH RUTHENIUM MODIFIED SURFACE
E. Frolova*, M. Ivanovskaya*, V.A. Sadykov, G.M. Alikina, A.I. Lukashevich, S. Neophytides**
(*Research Institute for Physical Chemical Problems, Belarusian State University, Minsk, Belarus; **Institute of Chemical Engineering and High- Temperature Processes, Patras, Greece)
Prog. Solid State Chem.,
33(2-4) (2005) pp. 317-325.
Structural peculiarities of Ce–Zr–La–O and Ce–Zr–La–O/Ru samples in mean of catalytic properties are compared. The samples (Ce:Zr = 1:1, La = 10÷30 mol.%, Ru = 1.5 wt.%) were obtained by sol–gel method (X-samples) and co-precipitation (P-samples). It is shown that Ce0.45Zr0.45La0.1O2δ//Ru X-samples are characterized by high thermal stability and the highest catalytic activity in partial methane oxidation reaction. According to XRD, BET, FTIR, EPR and XPS data it is concluded that the difference in the samples catalytic activity is caused by various disposition of Ru-containing phase on the support surface. The distinction in the dimension of Ru-containing particles (3D or 2D) is conditioned by structural peculiarities of Ce0.45Zr0.45La0.1O2δ and Ce0.35Zr0.35La0.3O2δ P- and X-samples.
SYNTHESIS AND SINTERING OF CERAMIC NANOCOMPOSITES WITH HIGH MIXED CONDUCTIVITY
V.V. Zyryanov*, V.A. Sadykov, M.I. Ivanovskaya**, J.M. Criado***, S. Neophytides****
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Belarusian State University, Minsk, Belarus; ***Seville University, Seville, Spain; ****Institute of Chemical Engineering & High Temperature Processes, Patras, Greece)
Sci. Sintering, 37(1) (2005) pp. 45-54.
Metastable solid solutions of complex oxides with fluorite and perovskite structures are obtained by mechanosynthesis. Dense ceramics on the base of these metastable phases was obtained by thermal sintering of nanopowders due to kinetic stabilization. Different degrees of a chemical interaction (interdiffusion) are observed during sintering of “perovskite+fluorite” and “perovskite+perovskite” composites. It is shown, that optimization of the composition, mixing conditions of individual phases and their sintering, preparation of ceramic composites with mixed conductivity for use in catalytic membrane reactors is possible. Unusual behavior of complex perovskites and fluorites is discovered during sintering, enabling determination of an optimum sintering temperature and time for which a qualitative explanation is given. It is established that rearrangement of fine crystalline particles as a whole plays a key role in shrinkage.
NANOCRYSTALLINE CATALYSTS BASED ON CeO2-ZrO2 DOPED BY PRASEODYMIUM OR GADOLINIUM: SYNTHESIS AND PROPERTIES
V.A. Sadykov, Yu.V. Frolova-Borchert, N.V. Mezentseva, G.M. Alikina, A.I. Lukashevich, E.A Paukshtis, V.S. Muzykantov, L.Ch. Batuev, T.G. Kuznetsova, E.M. Moroz, D.A. Zyuzin, V.P. Kolko, E.B. Burgina, V.V. Kriventsov, D.I. Kochubey, E. Kemnitz*, K. Scheurell*
(*Humboldt University, Berlin, Germany)
Mater. Res. Soc. Symp. Proc., 900E (2006) 0900-O10-04.1-04.6.
The structural features of nanocrystalline samples of Pr- or Gd-doped ceria-zirconia solid solutions prepared by polymerized precursor (Pechini) route and calcined at 500°C were studied using XRD, EXAFS, Raman, while their surface features before and after Pt supporting were characterized by IR spectroscopy of adsorbed CO test molecules. Effect of the nature and content of a dopant on the structural and surface features of studied systems as related to the oxygen mobility and catalytic activity in the reaction of methane selective oxidation into syngas at short contact times was considered. sphere. Despite this interaction, nanocomposites possess a high conductivity along with a high lattice oxygen mobility and reactivity. The addition of CoO improves sintering of nanocomposites.
DOPED CERIA - LaMeO3 (Me=Mn, Fe, Co) NANOCOMPOSITES: SYNTHESIS VIA MECHANOCHEMICAL ACTIVATION ROUTE AND PROPERTIES
Mater. Res. Soc. Symp. Proc., 885E (2006) A03-04 83-04 88.
Nanocomposite materials composed of fluorite and perovskite phases were prepared by mechanical treatment of the mixture of industrial raw material – mixed lanthanide oxide and 3d oxide followed by calcinations in the range of 900-1100°C. Samples were investigated with XRD, TEM, BET, IR, Raman and H2 TPR. Composites demonstrate a high lattice oxygen mobility and reactivity exceeding that of individual phases, being rather insensitive to calcination temperature.
DESIGN OF MULTILAYERED CERAMIC MIEC MEMBRANES
V.V. Zyryanov*, V.A. Sadykov
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Desalination, 199(1-3) (2006) pp. 299-301.
Nanopowders of LaGaO3- and LaMnO3-based complex perovskites P and ceria based fluorites F are derived by mechanosynthesis. Compatible nanocomposites F+P and P+P with MIEC properties were prepared and sintered at moderate temperatures up to dense ceramics. Obtained materials were studied by means of XRD, electrical conductivity measurements, TP reduction by methane and TP oxidation. New strategy based on facilities of mechanochemical ceramic approach is proposed to design multilayer ceramic membranes for CMR. Casting technology and one step sintering were used for production a thin film membrane with MIEC properties on porous substrate. Large fraction of as-milled powders from agglomerates with density
~70% was used for porous substrate and fine fractions of aggregates with sizes <1 μm were used in preparation of composites for thin dense films. Ceria based composites derived by Pechini route and/or mechanochemical approach are proposed as materials for protected thin films.
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, Yusung, 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.
PECULIARITIES OF FORMATION OF CARBON NANOFILAMENTS WITH VARIOUS CRYSTALLOGRAPHIC STRUCTURE FROM HYDROCARBONS OVER THE CATALYSTS CONTAINING IRON SUBGROUP METALS
V.V. Chesnokov, R.A. Buyanov
Crit. Technol. Membranes, 28(4) (2005) pp. 75-79.
Electron microscopy and XRD were used to study the mechanism of formation of carbon filaments from hydrocarbons in the presence of iron subgroup metal catalysts. Carbon nanofilaments with a coaxial-conical structures form from hydrocarbons on the NiAl2O3, Ni/MgO catalysts in a temperature range of 400-600°C. The kinetic curves of growth of filamentous carbon exhibit four periods such as induction, acceleration, stationary and deactivation. The reasons and processes providing transformation of catalytic particles and morphology itself of the filamentous carbon in each period of growth of the filamentous carbon has been established. It is possible to synthesize three “basic” structure types of graphite filaments depending on the properties of a catalyzing metal particle and conditions of the process performance. The work gives an explanation of the reasons and features of formation of three main types of carbon filaments. It is shown that the properties of metal particles are significantly controlled by methods of their preparation and additives of other metals. Note that the lattice parameters and some other characteristics of the alloyed particles, affecting both crystallographic and morphological properties of graphite filaments, change. The models of growth of carbon filaments with different crystallographic structures are presented.
ON THE MECHANISM OF FORMATION OF CARBON NANOFILAMENTS DURING CATALYTIC DECOMPOSITION OF HYDROCARBONS OVER IRON SUBGROUP METALS
R.A. Buyanov, V.V. Chesnokov
Catal. Ind., 2 (2006) pp. 3-15.
The progress in the science and technology is related to design of new composite materials, in particular, carbon filaments and fibers based products. In recent 20 years, the scientists paid special attention to a possibility of producing a new generation of such products as carbon nanosized filaments by various methods. The achievement of the optimal conditions requires the knowledge of the process mechanism to choose a catalyst, starting hydrocarbon raw material, and the process conditions. The review proposed generalizes the results of the complex investigations of regularities of carbon nanofilament formation during catalytic decomposition of hydrocarbons over iron- subgroup metals according to the “carbide cycle” mechanism. The process of production of these materials is shown to consist of two stages: chemical (catalytic) and physical ones. Four periods: induction, acceleration, stationary, and inactivation were defined in the course of generation and growth of carbon nanofilaments. The nature, mechanisms, and regularities of the stages and periods are explained. The scientific principles of carbon nanofilaments of various crystallographic characteristics were formulated.
EFFECT OF ZINC ADDED TO THE Co/Al2O3 CATALYST ON THE FORMATION OF CARBON NANOFILAMENTS FROM METHANE AND BUTADIENE-1,3
V.V. Chesnokov, R.A. Buyanov, I.V. Mishakov, V.I. Zaikovskii
Kinet. Catal., 47(3) (2006) pp. 445-450.
The dynamics of carbon nanofilament growth from methane and butadiene-1,3 on Co-Zn/Al2O3 catalysts have been studied in the temperature range 500–750°C. The rate-limiting step in the growth of nanofilaments from butadiene is carbon atom diffusion through the bulk of the metal particle. In the case of methane, the process is controlled by one of the stages of hydrocarbon decomposition on the metal particle. The structure and morphology of the nanofilaments (composites) forming by the carbide cycle mechanism on fine zinc-promoted cobalt particles have been studied by electron microscopy and X-ray diffraction. The morphology and crystallographic properties of the nanofilaments depend on the ratio of the hydrocarbon decomposition rate (which is determined by the nature of the hydrocarbon) to the rate at which carbon atoms diffuse from their formation sites to the nanofilament formation sites (which is determined by the nature of the metal particle and by the carbon diffusion coefficient in the particle bulk). The properties of the resulting carbon nanofilaments can be controlled by varying the nature of the hydrocarbon to be decomposed and the reaction temperature and by introducing another metal into the cobalt particles.
PROPERTIES OF INDIVIDUAL FRACTIONS OF DETONATION NANODIAMOND
I.S. Larionova*, V.L. Kuznetsov, A.V. Frolov*, O. Shenderova**, S.I. Moseenkov, I.N. Mazov
(*FGUP “Federal Research and Production Centre” “Altay”, Biysk, Russia; **International Technology Center, Raleigh, USA)
Diamond Relat. Mater., 15 (2006) рр. 1804-1808.
Detonation nanodiamonds synthesized and purified on an industrial scale were additionally purified and separated into narrow size fractions by centrifugation. The average particle size for the smallest fraction was lower than 30 nm and the yield was about 20 wt.%. Using FTIR spectra analysis, it was demonstrated that ND aggregates of different sizes, separated from the same pristine ND, have different surface compositions of active surface groups, particularly oxygen-containing groups, which finally influence their zeta potential values and hydrosol stability. Using DTA analysis, the higher reactivity of the smallest fractions during heat treatment in air was also demonstrated.
THE THERMAL STABILITY OF NANODIAMOND SURFACE GROUPS AND ONSET OF NANODIAMOND GRAPHITIZATION
Yu.V. Butenko, V.L. Kuznetsov, E.A. Paukshtis, A.I. Stadnichenko, I.N. Mazov, S.I. Moseenkov, A.I. Boronin, S.V. Koscheev
Fullerenes, Nanotubes, Carbon Nanostruct., 14(2-3) (2006) pp. 557-564.
The results of study of the surface chemistry of nanodiamonds treated by a mixture of HClO4 and H2SO2 acids are presented. Changes of the composition of surface diamond groups brought up by thermal annealing were monitored by Fourier transformed infrared spectroscopy and temperature- programmed desorption. The decomposition of oxygen-containing groups is observed at 300–900°C; CHx groups decompose at 700–1150°C. The process of the annealing of ND was investigated by the X-ray photoelectron spectroscopy. The clear onset of ND graphitization was observed at temperature of 950°C that is supported by the appearance of sp2 component in the C1s spectrum. The presence of the N1s peak in spectra of ND is observed in initial and partially graphitized ND annealed up to 1100°C.
WHO SHOULD BE GIVEN THE CREDIT FOR THE DISCOVERY OF CARBON NANOTUBES?
M. Monthioux*, V.L. Kuznetsov
(*CEMES, Toulouse Cedex, France)
Carbon, 44(9) (2006) pp. 1621-1623.
Due to a unique combination of physical properties and potential applications, carbon nanotubes have evolved into one of the hottest research topics today. Most publications on nanotubes refer back to the article by Sumio Iijima, published in Nature 354 (1991) 56, which started the present "nanotube boom". This article reviews some of the earlier publications, which reported likely synthesis and observation of nanotubes and related filamentous structures. The finite list of references will probably inspire further discussion. In spite of several inaccurate technical statements, this intriguing review makes a point by illustrating that a discovery often needs to await its time to cause a large societal impact.
ELECTRON-ELECTRON INTERACTION IN CARBON NANOSTRUCTURES
A.I. Romanenko*, O.B. Anikeeva*, T.I. Buryakov*, E.N. Tkachev*, A.V. Okotrub*, V.L. Kuznetsov, A.N. Usoltseva, A.S. Kotosonov**
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Institute of Carbon, Moscow, Russia)
Сond. Mat., (2006) 0608437.
The electron-electron interaction in carbon nanostructures was studied. A new method which allows to determine the electron-electron interaction constant λ from the analysis of quantum correction to the magnetic susceptibility and the magnetoresistance was developed. Three types of carbon materials: arc-produced multiwalled carbon nanotubes (arc-MWNTs), CVD- produced catalytic multiwalled carbon nanotubes (c- MWNTs) and pyrolytic carbon were used for investigation. It was found that λ=0.2 for arc-MWNTs (before and after bromination treatment); λ=0.1 for pyrolytic graphite; λ > 0 for c-MWNTs. It was concluded that the curvature of graphene layers in carbon nanostructures leads to the increase of the electron- electron interaction constant λ.
QUASI-TWO-DIMENSIONAL CONDUCTIVITY AND MAGNETOCONDUCTIVITY OF GRAPHITE-LIKE NANOSIZE CRYSTALLITES
A.I. Romanenko*, O.B. Anikeeva*, V.L. Kuznetsov, A.N. Obrastsov**, A.P. Volkov**, A.V. Garshev**
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Moscow Lomonosov State University, Moscow, Russia)
Solid State Commun., 137(11) (2006) рр. 625–629.
The temperature dependence of electrical conductivity and magnetoconductivity of new type of carbon films composed of nanosize thin graphite-like crystallites were investigated at temperature interval of 4.2–300 K and in the magnetic field range of 0–12 kG at 4.2 K, respectively. The crystallites consist of several (5–50) graphene layers which have predominant orientation perpendicularly to a film surface. At temperature ≤30 K the logarithmic conductivity decreases linearly with temperature. The positive magnetoconductivity of the films was observed in a magnetic field directed perpendicularly to the film surface in all intervals of field values. In magnetic field B≥4 kG the logarithmic asymptotic of conductivity from magnetic field was observed. That is characteristic of the systems with two-dimensional quantum corrections to magnetoconductivity. In a magnetic field directed along a film surface, the crossover from negative to positive magnetoresistivity is observed at B ≥ 8 kG.
THERMAL BEHAVIOR OF FLUORINATED DOUBLE-WALLED CARBON NANOTUBES
L.G. Bulusheva*, P.N. Gevko*, A.V. Okotrub*, Yu.V. Lavskaya*, N.F. Yudanov, L.I. Yudanova*, O.G. Abrosimov, E.M. Pazhetnov, A.I. Boronin, E. Flahaut**
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Centre Interuniversitaire de Recherche et d'Ingenierie des Materiaux, Université Paul-Sabatiér, Toulouse cedex, France)
Chem. Mater., 18(20) (2006) pp. 4967-4971.
Double-walled carbon nanotubes (DWNTs), produced by a catalytic chemical vapor deposition method, have been fluorinated using a volatile mixture of BrF3 and Br2. Optical absorption spectroscopic study on the product detected nonfluorinated nanotubes, which could correspond to the inner walls of DWNTs. The fluorinated DWNTs have been annealed in vacuum at fixed temperatures, and X-ray photoelectron spectroscopy showed almost no fluorine in the sample heated to 300°C. Comparison between X-ray fluorescent C K spectra of the pristine DWNT sample and the annealed fluorinated sample revealed change of the atomic structure of graphitic shells in the process of thermal defluorination.
CARBON FILMS GROWN ON Pt(1 1 1) AS SUPPORTS FOR MODEL GOLD CATALYSTS
D.E. Starr*, E.M. Pazhetnov, A.I. Stadnichenko, A.I. Boronin, S.K. Shaikhutdinov*
(*Department of Chemical Physics, Fritz-Haber Institute, Berlin, Germany)
Surf. Sci., 600(13) (2006) pp. 2688-2695.
Carbon films were grown on a Pt(1 1 1) single crystal by ethylene decomposition at elevated temperatures (1000–1300 K). Depending on the preparation conditions, different carbon structures formed on the metal surface such as flat and curved graphitic layers, carbon particles and carbon nanowires. Although these carbon films exhibited a high density of surface defects, gold interacted only weakly with the carbon surface. CO adsorption on the Au/carbon systems was very similar to that observed for various Au/oxide systems previously studied. This finding strongly indicates that CO adsorption on gold is essentially independent of the nature of support.
XPS STUDY OF CARBON FILMS ON THE Pt(III) SURFACE OBTAINED BY HIGH TEMPERATURE DECOMPOSITION OF METHANE AND ETHYLENE
E.M. Pazhetnov, A.I. Boronin
Chem. Sustain. Devel., 14(6) (2006) pp. 599-603.
The carbon films grown on Pt(III) surface by the high temperature catalytic decomposition of methane and ethylene were investigated with aid of X-ray photoelectron spectroscopy (XPS). It was observed that photoelectron spectra of carbon films depend on the hydrocarbon used as a reagent. It was shown that in case of methane used as the reagent the flat graphite films are deposited on the Pt(III) surface while ethylene or ethylene/methane mixture stimulates the carbon films distortion resulting in curved fullerites/like structures. The formation of curved carbon films occurs through the formation of flat graphenes as the intermediate structures. It was determined that this topographic transition is reversible and has dynamic character depending on the crystal temperature and ethylene presence in the gas phase. The role of the diffusion-segregation phenomenon of carbon atoms in the formation of the curved films was established.
CHEMICAL PROPERTIES OF THE SURFACE OF NANOFIBROUS CARBONACEOUS MATERIALS PRODUCED BY CATALYTIC METHANE DECOMPOSITION
M.A. Ermakova, D.Yu. Ermakov, V.V. Kaichev, G.G. Kuvshinov*
(*Novosibirsk State Technical University, Novosibirsk, Russia)
Russ. J. Phys. Chem. 80(6) (2006) pp. 886-891.
The chemical behavior of nanofibrous carbonaceous materials prepared by the catalytic decomposition of methane was studied by IR spectroscopy, X-ray photoelectron spectroscopy, and titration. Initial carbon was shown to be virtually devoid of functional groups on its surface. Treatment of carbonaceous samples with alkali, ammonia, or nitric acid modified the surface of carbon and increased the number of functional groups.
STUDYING OF THE STRUCTURE OF POROUS CARBON NANOFIBRES AND SUPPORTED Pd PARTICLES
N.V. Chesnokov*, B.N. Kuznetsov*, N.M. Mikova*, V.A. Drozdov*, V.I. Zaikovskii
(*Institute of Chemistry and Chemical Technology, Krasnoyarsk, Russia)
Russ. Chem. J. (Mendeleev Chem. J.), 50(1) (2006) pp. 104-106.
Texture properties of porous carbon nanofibres, size of supported Pd particles and character of their distribution are studied. Texture properties of porous carbon nanofibres were studied by electron microscopy and adsorption analysis. It is established, that homogeneous Pd distribution in pores of support is achieved due to developed nanoporous structure presented by pores of practically uniform size. Supported Pd particles are 4-5 nm in size.
SPECTROSCOPY OF SMOOTH DEUTERATED CARBON FILMS REDEPOSITED FROM PLASMA DISCHARGE IN THE TOKAMAK T-10
N.Yu. Svechnikov*, V.G. Stankevich*, A.M. Lebedev*, K.A. Men’shikov*, B.N. Kolbasov*, V.V. Kriventsov
(*Russian Research Centre Kurchatov Institute, Moscow, Russia)
Crystallogr. Rep., 51(Suppl. 1) (2006) pp. 158-162.
Smooth deuterated carbon films redeposited from a deuterium plasma discharge in the tokamak T 10 vacuum chamber have been investigated by different spectroscopic methods and temperature measurements. The photoluminescence excitation spectra of sp3–sp2 nanostructures of tokamak films and sp2 nanostructures of fullerite C60 films are compared. The effect of defect states on the photoluminescence and its temperature quenching is discussed. It is concluded that the mechanism of thermal luminescence quenching for Smooth deuterated tokamak films is close to the corresponding mechanism for amorphous a-C:H films.
PORE SIZE DISTRIBUTION ANALYSIS OF ACTIVATED CARBONS: APPLICATION OF DENSITY FUNCTIONAL THEORY USING NONGRAPHITIZED CARBON BLACK AS A REFERENCE SYSTEM
E.A. Ustinov*, D.D. Do**, V.B. Fenelonov
(*Scientific and Production Complex “Provita”, St. Petersburg, Russia; **University of Qucensland, Brisbane, Australia)
Carbon, 44(4) (2006) pp. 653-663.
The application of nonlocal density functional theory (NLDFT) to determine pore size distribution (PSD) of activated carbons using a nongraphitized carbon black, instead of graphitized thermal carbon black, as a reference system is explored. It was shown that in this case nitrogen and argon adsorption isotherms in activated carbons are precisely correlated by the theory, and such an excellent correlation would never be possible if the pore wall surface was assumed to be identical to that of graphitized carbon black. It suggests that pore wall surfaces of activated carbon are closer to that of amorphous solids because of defects of crystalline lattice, finite pore length, and the presence of active centers, etc. Application of the NLDFT adapted to amorphous solids resulted in quantitative description of N2 and Ar adsorption isotherms on nongraphitized carbon black BP280 at their respective boiling points. In the present paper it is determined solid-fluid potentials from experimental adsorption isotherms on nongraphitized carbon black and subsequently used those potentials to model adsorption in slit pores and generate a corresponding set of local isotherms, which were used to determine the PSD functions of different activated carbons.
MAGNETORESISTANCE AND RESISTANCE VERSUS TEMPERATURE DEPENDENCE OF A MESOPOROUS MESOPHASE CARBON
S. Sassine*, E.B. Olshanetsky*, Z.D. Kvon*, M.S. Melgunov, E.A. Melgunova, J.C. Portal**
(*Institute of Semiconductors Physics, Novosibirsk, Russia; **High Magnetic Fields Laboratory, Grenoble, France)
Physica E - Low-Dimensional Syst. & Nanostruct., 34(1-2) (2006) pp. 655-657.
In the present work the transport properties of mesoporous mesophase carbon (MMC) powder have been investigated in wide temperature and magnetic field ranges. It has been found that in the range 1.5-42 K the temperature dependence of the resistivity of this material can be described by Efros-Shklovskii variable range hopping law. In the same temperature range the magnetoresistance is positive but does not fit the exponential dependence expected in the hopping regime.
CATALYTIC OXIDATION OF 2,3,6-TRIMETHYLPHENOL AND 2-METHYLNAPHTHOL-1 INTO CORRESPONDING PARA-QUINONES BY DIOXYGEN IN THE PRESENCE OF Mo-V-PHOSPHORIC HETEROPOLY ACID SOLUTIONS AS KEY STAGES OF TOCOPHEROL AND K VITAMIN SYNTHESIS
E.G. Zhizhina, V.F. Odyakov, K.I. Matveev
Catal. Ind., 6 (2005) pp. 19-27.
Solutions of Mo-V-phosphoric heteropoly acids (HPA) are efficient catalysts for oxidation of alkyl phenols of benzene and naphthalene series by dioxygen into corresponding alkyl-1,4-quinones. The most important reactions are oxidation of 2,3,6-trimethylphenol (TMP) into 2,3,5-trimethyl-1,4- benzoquinone (TMQ, key intermediate product of tocopherol synthesis) and oxidation of 2-methylnaphthol-1 into 2-methyl-1,4-naphthoquinone (vitamin K3). In industry, TMP is oxidized into TMQ by dioxygen in the presence of copper chlorides. The disadvantage of such a catalyst is its chlorinating ability. In any case, ecologically dangerous chlorinated quinones (related to dioxins) must be thoroughly separated and detoxified. In the industry, vitamin K3 is produced by uncatalyzed oxidation of 2-methylnaphthalene by chromic acid. Both oxidation processes are non-ecological. They became long- outdated. In the presence of HPA, the oxidation is carried out at 50÷60°C in two-phase systems (aqueous solution of HPA + solution of substrate and product in organic solvent). The product is separated from the catalyst by phase separation. The TMQ selectivity reaches 99%, and vitamin K3 selectivity - 90%. Such high characteristics allow to use TMQ without purification in following stages of tocopherol synthesis, to lower the number of operations, and to obtain more pure final product. The method proposed for TMQ synthesis may be taken as a basis of an ecological technology of tocopherol preparation. The method proposed for vitamin K3 synthesis by oxidation of 2-methylnaphthol-1 in the presence of HPA was used for development of a low-waste process “Vikasib” for synthesis of K group vitamins at the Boreskov Institute of Catalysis. In this article results of investigations of development of new ecological catalytic methods of tocopherol and vitamin K3 synthesis are presented.
PRODUCTION OF K3 VITAMIN BY THE REACTION OF DIENE SYNTHESIS IN THE PRESENCE OF THE SOLUTIONS OF Mo-V-PHOSPHORIC HETROPOLY ACIDS AS CATALYSTS
M.V. Simonova, Е.G. Zhizhina, K.I. Matveev, V.V. Russkikh*
(*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Academy Proceed., Chem. Chem. Techn., 49(9) (2006) pp. 20-23.
The principal opportunity of preparation of vitamin K3 (2-methyl-1,4-naphthoquinone) from such accessible substrates as 2-methylphenol (o-cresol) or 2-methylaniline (o-toluidine) is shown. These processes proceed by reaction of diene synthesis. Solutions of Mo-V-phosphoric hetropoly acids are polyfunctional catalysts of such processes. It allows to carry out oxidation and diene synthesis by one technological stage. Solutions of catalysts are regenerated at 140-160°C under O2 pressure.
KINETICS AND MECHANISM OF THE WET OXIDATION OF PROPENE TO ACETONE IN THE PRESENCE OF Pd2+ IONS AND Mo-V-PHOSPHORIC HETEROPOLY ACIDS
E.G. Zhizhina, M.V. Simonova, V.F. Odyakov, K.I. Matveev
React. Kinet. Catal. Lett., 89(1) (2006) pp. 157-166.
Oxidation of propene to acetone in water solutions in the presence of homogeneous catalysts (Pd2+ + HPA-x, where HPA-x = H3+xPVxMo12-xO40, x = 1−4) is studied. This reaction is shown to be of 1st order with respect to C3H6 and of the 0.5th order with respect to Pd. The reaction rate does not depend on the concentration of HPA-x and acidity of the catalyst solution. The apparent activation energy of the reaction is 21 kJ/mol. A reaction mechanism is proposed.
H2O2 AND O2/H2 OXIDATION OF AROMATIC COMPOUNDS IN CATALYTIC SYSTEMS CONTAINING HETEROPOLY COMPOUNDS
N.I. Kuznetsova, N.V. Kirillova, L.I. Kuznetsova, M.Yu. Smirnova, V.A. Likholobov*
(*Institute of Hydrocarbons Processing, Omsk, Russia)
In “Environmental Applications of Advanced Oxidation Processes”, Chania, 2006, e-Proceedings, 158 (8 pages).
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.
INTERACTION OF PLATINUM AND MOLYBDOPHOSPHORIC HETEROPOLY ACID UNDER CONDITIONS OF CATALYST PREPARATION FOR BENZENE OXIDATION TO PHENOL WITH AN O2-H2 GAS MIXTURE
L.I. Kuznetsova, N.I. Kuznetsova, S.V. Koscheev, V.A. Rogov, V.I. Zaikovskii, B.N. Novgorodov, L.G. Detusheva, V.A. Likholobov*, D.I. Kochubey
(*Institute of Hydrocarbons Processing, Omsk, Russia)
Kinet. Catal., 47(5) (2006) pp. 704-714.
The transformations of platinum and a heteropoly acid (HPA) in binary systems prepared from H2PtCl6 or H2PtCl4 and H3PMo12O40 were studied using IR and UV–VIS spectroscopy, elemental analysis, XPS, EXAFS, TPR, and HREM. The calcination of platinum chloride with the HPA to 450°C resulted in the formation of a platinum salt of the HPA along with decomposition products (mixture I). The reduction of calcined samples containing Pt : HPA = 1 : 1 with hydrogen at 300°C (mixture II) followed by exposure to air resulted in the regeneration of the HPA structure. The resulting solid samples of (Pt01-n PtIInClmOxHy)⋅(H3+pPMoVI12-pMoV O40 ) (III) contained platinum and molybdenum in both oxidized and reduced states. The following association species were isolated from mixtures I and II by dissolving in water: [PtIIn⋅PMo12O40], (Is) (n = 0.3–0.8) and [Pt0n PMoвос12O40] (IIs) (n 1). Under exposure to air, the solutions of Is were stable (pH ~2), whereas Ptmet was released from IIs. After the drying of Is, the solid association species (PtIInClmOxHy) (H3PMo12O40), where n = 0.3-0.8, m = 0.2-1, and x = 3–0, (Isolid) were obtained. The Isolid/SiO2 supported samples were prepared by impregnating SiO2 with a solution of Is and drying at 100°C. Platinum metal particles of size ~20 Å and a mixed-valence association species of platinum with the HPA were observed after the reduction of Isolid/SiO2 with hydrogen at 100–250°C. These samples were active in the gas-phase oxidation of benzene to phenol at 180°C with the use of an O2–H2–N2 mixture.
CATALYTIC OXIDATION OF OLEFINS AND ALCOHOLS WITH HYDROGEN PEROXIDE IN A TWO-PHASE SYSTEM GIVING MONO- AND DICARBOXYLIC ACIDS
Z.P. Pai, A.G. Tolstikov, P.V. Berdnikova, G.N. Kustova, T.B. Khlebnikova, N.V. Selivanova, A.B. Shangina, V.G. Kostrovskii*
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Russ. Chem. Bull., 54(8) (2005) pp. 1847-1854.
The present study considered the influence of various factors on the catalytic activity of systems based on a combination of tetrakis(oxodiperoxotungsto)phosphate(3–) with quaternary ammonium cations, for example, with methyltri-n-octylammonium [Me(n-C8H17)3N]+. The catalysts were tested in oxidation of cycloolefins (cyclohexene and cyclooctene), alcohols (octan-1-ol and phenylmethanol), and unsaturated fatty acids (cis-9-octadecenoic and 12-hydroxy-9Z-octadecenoic acids) with a 30% hydrogen peroxide solution. These reactions proceed under mild conditions (atmospheric pressure, 80-90°C) to give carboxylic acids. The catalytic systems were characterized by vibrational (IR and Raman) spectroscopy. The state of the systems formed from various precursors, viz., polyoxometallates and phase-transfer catalysts, was studied. It was demonstrated for the first time that the structure formation of peroxo complexes depends on the nature of the halide anion of the quaternary ammonium salt used. The melting points of individual catalytic complexes were determined. The optimal conditions for oxidation were found.
PHASE-TRANSFER CATALYTIC OXIDATION OF THE ORGANIC COMPOUNDS WITH THE HYDROGEN PEROXIDE IN THE PRESENCE OF PEROXOPOLYOXOMETALLATES
Z.P. Pai, P.V. Berdnikova, A.G. Tolstikov, T.B. Khlebnikova, N.V. Selivanova
Catal. Ind., 5 (2006) pp. 12-23.
Modern approaches to the development of ecologically and economically acceptable methods of manufacturing of industrially important large-tonnage organic products or fine chemicals with the use of petrochemistry products and renewable raw materials are considered in the presented review. The prospects of the application of phase-transfer catalysis (PTC) method in organic synthesis are shown in the introduction. In the part of the review concerning catalysts the comparison of data on the synthesis of catalytic systems on the base of peroxopolyoxometalates in combination with phase- transfer catalysts applied for the catalytic oxidation of organic compounds including compounds with double bonds and asymmetric centers is carried out. In the part concerning carboxylic acids manufacturing the analysis of tradition processes of their production and the market needs is performed. With the purpose to demonstrate the advantages of the carboxylic acids one-stage producing the examples of the oxidation of cyclic olefins, alcohols and unsaturated fatty acids in two-phase solutions with the use of the PTC method are given.
H2O2-BASED OXIDATION OF FUNCTIONALIZED PHENOLS CONTAINING SEVERAL OXIDIZABLE SITES TO p-QUINONES USING A MESOPOROUS TITANIUM-SILICATE CATALYST
O.V. Zalomaeva, O.A. Kholdeeva, A.B. Sorokin*
(*Institut de Recherches sur la Catalyse, Villeurbanne, France)
Green Chem., 8 (2006) pp. 883-886.
The oxidation of 2-allylphenol and different phenols bearing alcohol functional groups with aqueous H2O2 as oxidant and heterogeneous titanium- silicate Ti-MMM-2 as catalyst exhibits an unusual selectivity affording the corresponding p-quinones with good to moderate yield and keeping the other oxidizable sites intact. The use of hydrogen peroxide and heterogeneous titanium-silicate catalyst is a green alternative to the stoichiometric oxidation with hypervalent iodine compounds that provides better yields of structurally complex quinones in one step.
ZrIV-MONOSUBSTITUTED KEGGIN-TYPE DIMERIC POLYOXOMETALATES: SYNTHESIS, CHARACTERIZATION, CATALYSIS OF H2O2-BASED OXIDATIONS, AND THEORETICAL STUDY
O.A. Kholdeeva, G.M. Maksimov, R.I. Maksimovskaya, M.P. Vanina, T.A. Trubitsina, D.Yu. Naumov*, B.A. Kolesov*, N.S. Antonova**, J.J. Carbó**, J.M. Poblet**
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Universitat Rovira i Virgili, Tarragona, Spain)
Inorg. Chem., 45(18) (2006) pp. 7224-7234. The previously unknown ZrIV-monosubstituted Keggin-type polyoxometalates (Zr-POMs), (n-Bu4N)7H[{PW11O39Zr(μ-OH)}2] (1), (n-Bu4N)8[{PW11O39Zr(μ-OH)}2] (2), and (n-Bu4N)9[{PW11O39Zr}2(μ-OH)(μ-O)] (3) differing in their protonation state, have been prepared starting from heteropolyacid H5PW11ZrO40·14H2O. The compounds were characterized by elemental analysis, potentiometric titration, X-ray single-crystal structure, and IR, Raman, and 31P and 183W NMR spectroscopy. The single-crystal X-ray analysis of 2 reveals that two Keggin structural units [PW11O39Zr]3- are linked through two hydroxo bridges Zr-(OH)-Zr with ZrIV in 7-fold coordination. The IR spectra of 1 and 2 show a characteristic band at 772 cm-1, which moves to 767 cm-1 for 3, reflecting deprotonation of the Zr-(OH)-Zr bond. Potentiometric titration with methanolic Bu4NOH indicates that 1-3 contain 2, 1, and 0 acid protons, respectively. 183W NMR reveals Cs symmetry of 2 and 3 in dry MeCN, while for 1, it discovers nonequivalence of its two subunits and their distortion resulting from localization of the acidic proton on one of the Zr-O-W bridging O atoms. The 31P NMR spectra of 2 and 3 differ insignificantly in dry MeCN, showing only signals at δ-12.46 and -12.44 ppm, respectively, while the spectrum of 1 displays two resonances at δ-12.3 (narrow) and -13.2 (broad) ppm, indicating slow proton exchange on the 31P NMR time scale. The theoretical calculations carried out at the density functional theory level on the dimeric species 1-3 propose that protonation at the Zr-O-Zr bridging site is more favorable than protonation at Zr-O-W sites. Calculations also revealed that the doubly bridged hydroxo structure is thermodynamically more stable than the singly bridged oxo structure, in marked contrast with analogous Ti- and Nb-monosubstituted polyoxometalates. The interaction of 1-3 with H2O and H2O2 in MeCN has been studied by both 31P and 183W NMR. The stability of the [PW11O39ZrOH]4- structural unit toward at least 100-fold excess of H2O2 in MeCN was confirmed by both NMR and Raman spectroscopy. The interaction of 1 and 2 with H2O in MeCN produces most likely monomeric species (n-Bu4N)3+n[PW11O39Zr(OH)n(H2O)3-n] (n = 0 and 1) showing a broad 31P NMR signal at δ-13.2 ppm, while interaction with H2O2 leads to the formation of an unstable peroxo species (δ-12.3 ppm), which reacts rapidly with cyclohexene, producing 2-cyclohexen-1-one and trans-cyclohexane-1,2-diol. Both 1 and 2 show a pronounced catalytic activity in H2O2 decomposition and H2O2-based oxidation of organic substrates, including cyclohexene, α-pinene, and 2,3,6-trimethylphenol. The oxidation products are consistent with those of a homolytic oxidation mechanism. On the contrary, 3 containing no acid protons reacts with neither H2O nor H2O2 and shows negligible catalytic activity. The Zr-monosubstituted polyoxometalates can be used as tractable homogeneous probes of Zr single-site heterogeneous catalysts in studying mechanisms of H2O2-based oxidations.
TITANIUM-MONOSUBSTITUTED POLYOXOMETALATES: RELATION BETWEEN HOMOGENEOUS AND HETEROGENEOUS Ti-SINGLE-SITE-BASED CATALYSIS
O.A. Kholdeeva
Top. Catal., 40(1-2) (2006) рр. 229-243.
The similarity in the catalytic behaviour of titanium-monosubstituted Keggin type polyoxometalates [PTi(L)W11O39]n- (Ti-POMs) and heterogeneous titanium single-site catalysts in selective oxidations with H2O2 is demonstrated. Recent achievements in the application of Ti-POMs as soluble molecular models for studying mechanisms of oxidation catalysis are reviewed.
EXPERIMENTAL STUDY OF DIMETHYL METHYLPHOSPHONATE DECOMPOSITION OVER ANATASE TiO2
D.A. Trubitsyn, A.V. Vorontsov
J. Phys. Chem. B, 109(46) (2005) pp. 21884-21892.
Removal from air and decomposition of dimethyl methylphosphonate (DMMP) over high surface area anatase TiO2 at ambient temperature have been quantitatively studied by employing Fourier transform infrared (FTIR) technique under static conditions. In the first scenario of air purification, DMMP underwent reactive adsorption that upon completion was followed by photocatalytic oxidation. DMMP was captured over the TiO2 surface at the speed of external diffusion. Hydrolysis of adsorbed DMMP led to methanol and methyl methylphosphonate (MMP). At low DMMP coverage quantity, it hydrolyzed completely with the formation of completely surface- bound methanol at 1% relative humidity (RH) and mostly gaseous methanol at 50% RH. Photocatalytic oxidation generated CO2 as the only carbonaceous gaseous product and bidentate formates as the intermediate surface product. At high DMMP coverage quantity, it was captured incompletely and hydrolyzed partially with CH3OH in the gas phase only, 50% RH enhancing both processes. Photocatalytic oxidation generated gaseous HCOOH, CO, and CO2 and was incomplete due to catalyst deactivation by nonvolatile products. In the second scenario of air purification, DMMP underwent adsorption, hydrolysis, and photooxidation at the same time. It resulted in the quickest removal of DMMP from the gas phase and completion of oxidation in 30 min, suggesting this process for practical air decontamination. At least 0.8 nm2 of TiO2 surface per each DMMP molecule should be available for complete purification of air.
PHOTOINDUCED HETEROGENEOUS PROCESSES ON PHASE CHEMICAL COMPONENTS OF SOLID TROPOSPHERIC AEROSOLS
V.S. Zakharenko
Top. Catal., 35(3-4) (2005) pp. 231-236.
This work shows the results of photoinduced process investigations over some metal oxides of the semiconductor type (In2O3, Sc2O3, V2O5 and MoO3) and insulator type (MgO). These metal oxides can be the chemical phase components of solid tropospheric aerosols. The quantum yields and spectral dependencies of the quantum yields of photoadsorption and photocatalytic oxidation in the spectral region including the spectral region of solar tropospheric irradiation are determined.
ADSORPTION OF FREONS BY CALCIUM CARBONATE UNDER ATMOSPHERIC CONDITIONS
V.S. Zakharenko, A.N. Moseichuk*
(*Institute of Petroleum Chemistry, Tomsk, Russia)
Atmosph. Oceanic Optics, 18(5-6) (2005) pp. 454-458.
The process of interaction of halogen-containing organic compounds (Freons: 134a, 22, and 12) with calcium carbonate surface under illumination and conditions close to the tropospheric ones was studied. It is suggested that the interaction is a destructive photosorption of Freons (134a or 22). This interaction yields the surface calcium fluoride and calcium chloride. The spectral dependence of the effective quantum yield for Freon 134a is determined.
STUDY OF THE PHOTOINDUCED FORMOSE REACTION BY FLASH AND STATIONARY PHOTOLYSIS
O.A. Snytnikova*, A.N. Simonov, O.P. Pestunova, V.N. Parmon, Yu.P. Tsentalovich*
(*International Tomography Center, Novosibirsk, Russia)
Mendeleev Commun., 16(1) (2006) pp. 9-11.
The chemical condensation of formaldehyde into more complex aldehydes (glycolaldehyde and glyceraldehyde) and monosaccharides (glucose, lyxose, erythrose and erythrulose) under UV irradiation was found to proceed in acidic aqueous solutions in the absence of catalysts and initial primers.
HETEROGENEOUS FENTON SYSTEM FOR DEEP OXIDATION OF TOXIC ORGANIC SUBSTANCES IN WATER SOLUTIONS
O.A. Makhotkina, E.V. Kuznetsova, L.G. Matvienko, V.N. Parmon
Catal. Ind., 4 (2006) pp. 30-37.
The Fenton heterogeneous system FeZSM-5/H2O2 was investigated in deep oxidation of toxic organic contaminants, such as 1,1-dimethylhydrazine (NDMH), N-nitrosodimethylamine (NDMA), dimethyl keton, and others, in water solutions. Adsorption characteristics of FeZSM-5 with respect to H2O2, NDMH, NDMA, dimethyl keton, and ethanol as well as the kinetic behavior of NDMH catalytic oxidation by hydrogen peroxide were studied. An analysis of intermediate and final products of NDMH oxidation by hydrogen peroxide over FeZSM-5 was carried out. The system investigated is heterogeneous and ecologically safe. It provides more effective use of the oxidizer and a possibility of full oxidation of toxic organic compounds to harmless substances and it is very promising system for deactivation of water solutions.
CATALYTIC DETOXIFICATION OF 1,1-DIMETHYLHYDRAZINE AQUEOUS SOLUTIONS IN HETEROGENEOUS FENTON SYSTEM
O.A. Makhotkina, E.V. Kuznetsova, S.V. Preis*
(*Lappeenranta University of Technology, Lappeenranta, Finland)
Appl. Catal., B, 68(2-3) (2006) pp. 85-91.
The experimental study into catalytic properties of FeZSM-5 was undertaken into oxidation of 1,1-dimethylhydrazine (UDMH) aqueous solutions using hydrogen peroxide. The performances of heterogeneous and homogeneous Fenton systems were compared. UDMH complete mineralization was achieved. Formic and acetic acids, as well as nitromethane, were identified as oxidation by- products. Adsorption properties of FeZSM-5 with respect to hydrogen peroxide, 1,1-dimethylhydrazine and N-nitrosodimethylamine have been studied. The effects of the oxidant and the target compound concentrations, temperature and pH of aqueous solution were established
NOBLE METAL AND SULFURIC ACID MODIFIED TiO2 PHOTOCATALYSTS: MINERALIZATION OF ORGANOPHOSPHOROUS COMPOUNDS
E.A. Kozlova, A.V. Vorontsov
Appl. Catal., B, 63(1-2) (2006) pp. 114-123. Photocatalytic oxidation by oxygen of air in water suspension of TiO2-based catalysts was carried out for dimethyl methylphosphonate (DMMP) and trimethyl phosphate (TMP) — simulants of warfare agents. Active photocatalysts were prepared via surface modification of standard photocatalyst Degussa P25 with platinum and palladium. The developed catalysts were about three-fold more active than traditionally best photocatalyst Degussa P25. Kinetic curves of DMMP oxidation on TiO2 and Pt/TiO2 are well approximated by the Langmuir–Hinshelwood model with competitive adsorption of oxygen and organophosphorus compound. The increase of activity of Pt/TiO2 is linked with higher oxygen adsorption constant or reaction rate coefficient. Photocatalytic oxidation can be scaled up to a larger reactor with the same reaction rates expressed as mmol l−1 min−1 in mineralization of DMMP. The batch recirculating reactor with total volume 3 l utilizes photocatalyst deposited over porous support and demonstrated higher oxidation rate and catalyst stability compared to suspended photocatalyst. Main criteria for mass- transfer process in the batch recirculating reactor were calculated to understand how concentration cross gradient depends on flow rate. The concentration of oxygen in reaction mixture changed with the stirring or recirculation rate and exerts strong influence on the oxidation rate.
REGULARITIES OF DECOMPOSITION OF ORGANIC VAPORS USING A PHOTOCATALYTIC AIR CLEANER
I.A. Baturov, A.V. Vorontsov, D.V. Kozlov
Russ. Chem. Bull., 54(8) (2005) pp. 1866-1873.
The kinetics of oxidation of vapors of model air contaminators, viz., acetone, ethanol, and heptane, was studied using a photocatalytic air cleaner. The composition of the oxidation products was determined, and the rates of oxidation of the starting substances were measured. The deep oxidation of the starting substrates to CO2 and H2O occurs until their concentration achieves a limiting value. At higher concentrations a "breakthrough" of the starting substrate is observed. Ethanol is oxidized with the formation of intermediate products. The experimental data obtained were approximated by a kinetic model, which includes stages of formation of intermediates and their competitive adsorption. The results of the approximation agree well with the experimental data.
ELECTROCATALYTIC PROPERTIES OF Au(111)-Pd QUASI-SINGLE-CRYSTAL FILM ELECTRODES AS PROBED BY ATR-SEIRAS
S.N. Pronkin, M. Hara*, T. Wandlowski*
(*Institute for Thin Films and Interfaces ISG 3, Research Centre Juelich, Juelich, Germany)
Russ. J. Electrochem., 42(11) (2006) pp. 1177-1192.
Electrochemical and electrocatalytic properties of thin films Au(111-25 nm), which are quasi-single- crystal electrodes 25 nm thick made of gold with the (111) preferential orientation, and same electrodes modified with a monolayer (ML) of palladium are studied in 0.1 M solutions of HClO4 and H2SO4 employing voltammetric techniques and surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS). Spectroscopic experiments demonstrate strong adsorption of electrolyte species (H2O, OHads, anions) on the Pd surface. The weak and reversible adsorption of CO on Au(111-25 nm) does not change the interfacial-water structure. Adsorption of CO on the Pd-modified film results in an irreversibly adsorbed CO adlayer stabilized by co- adsorbed isolated water species. Various electrooxidation mechanisms are discussed. Electrochemical and spectroscopic investigations on the adsorption and electrooxidation of HCOOH on bare and 1 ML Pd–Au(111-25 nm) electrodes reveal that electrooxidation proceeds in both cases via a direct or dehydrogenation pathway. This mechanism involves the formation of formate as intermediate, which is detected by in situ ATR-SEIRAS. The reactivity on Pd-modified surfaces is higher than on bare gold. The specifically adsorbed anions (sulfate/bisulfate) and the oxide formation on the substrate surface lower the reactivity for CO and HCOOH on both surfaces.
ELECTROCRYSTALLIZATION OF Pt LAYERS ONTO Au SUBSTRATES; AN X-RAY DIFFRACTION STUDY
I.Yu. Molina, L.M. Plyasova, S.V. Cherepanova, E.R. Savinova, G.A. Tsirlina*
(*Moscow Lomonosov State University, Moscow, Russia)
Z. Kristallogr. Suppl., 23 (2006) pp. 293-298.
An X-ray diffraction study of the structural features of Pt electrodeposited on Au substrates was performed. The influence of the deposition potential, electrochemical ageing and model catalytic reactions on the structural characteristics of deposits has been analysed. It has been shown that under the conditions employed highly defective electrolytic deposits are formed composed of nm-sized particles (10–30 nm). Electrochemical ageing and model electrochemical reactions lead to the relaxation of the defect structure of electrodeposited Pt, which is expressed in an increase of lattice parameter and particle size and decrease in the values of strains and density of randomly distributed dislocations. The data obtained showed that the deposition potential is a key parameter determining structural characteristics of Pt electrolytic deposits, and allowed to reveal the minimum of intergrowth degree of Pt nano-particles.
ELECTRODEPOSITED PLATINUM REVISITED: TUNING NANOSTRUCTURE VIA THE DEPOSITION POTENTIAL
L.M. Plyasova, I.Yu. Molina, A.N. Gavrilov*, S.V. Cherepanova, O.V. Cherstiouk, N.A. Rudina, E.R. Savinova, G.A. Tsirlina*
(*Moscow Lomonosov State University, Moscow, Russia)
Electrochem. Acta, 51(21) (2006) pp. 4477-4488.
Pt nanostructured materials composed of nm-sized Pt crystallites interconnected via grain boundaries are prepared by electrochemical deposition on Au and glassy carbon substrates from aqueous chloride solutions of hexachloroplatinic acid under potentiostatic mode at various potentials (0.025–0.550 V versus RHE). These samples may be considered as model electrode materials for the investigation of the influence of structural defects in electrocatalysis. Nanostructure and morphology of electrodeposited materials are analyzed with X-ray diffractometry and scanning electron microscopy. Considerable distortions of Pt lattice are detected, which are revealed by the decreased lattice parameter and significant microstrains. These lattice distortions increase with the decrease of the deposition overvoltage, and are the highest in the region of kinetically controlled electrodeposition. The deposition potential can be thus used as a tool to tune the nanostructure of supported Pt. Defectiveness is found to correlate with the degree of surface screening estimated from the difference of the calculated and the experimental surface areas. Screening is found to result from both the crystal coalescence and the existence of nanopores. Continuous potential cycling is accompanied by restructuring of both nanoparticles and intergrain boundaries, but does not fully relax lattice compression.
TEMPERATURE DEPENDENCE OF THE OXYGEN REDUCTION KINETICS ON RuxSey/C CATALYSTS
D. Leveratto*, A. Racz*, E.R. Savinova, U. Stimming*
(* Technische Universität München, Garching, Germany)
Fuel Cells, 6(3-4) (2006) pp. 203–207.
The temperature dependence of the oxygen reduction kinetics on carbon-supported RuxSey catalysts is studied using a rotating disc electrode in 0.5 M H2SO4 in the temperature interval from 25°C to 65°C. When the absolute value of the overpotential is below ca. 0.65 V, the reaction is limited by a one- electron charge transfer step, where the transfer coefficient is independent of the temperature and equal to 0.44. The apparent activation enthalpy at zero overpotential is 0.49 eV and the pre-exponential factor is independent of the temperature.
SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF Se-MODIFIED CARBON-SUPPORTED Ru NANOPARTICLES FOR THE OXYGEN REDUCTION REACTION
V.I. Zaikovskii, K.S. Nagabhushana*, V.V. Kriventsov, K.N. Loponov, S.V. Cherepanova, R.I. Kvon, H. Boennemann**, D.I. Kochubey, E.R. Savinova
(*Forschungszentrum Karlsruhe, Postfach, Germany, **Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr, Germany)
J. Phys. Chem. B., 110(13) (2006) pp. 6881-6890.
This work is part of a continued research aimed at the understanding of the promoting role of Se in the enhancement of the electrocatalytic activity of Ru in the oxygen reduction reaction. The objective of this paper is to systematically investigate the transformation of Ru nanoparticles upon their modification with the increasing amounts of Se. The Se-modified Ru/C samples with Se:Ru ratio from 0 to 1 were prepared by reacting carbon-supported Ru nanoparticles with SeO2 followed by reductive annealing and characterized using high-resolution transmission electron microscopy, energy-dispersive X-ray, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure. The results suggest that Se strongly interacts with Ru, resulting in the chemical bond between Ru and Se and formation of Ru selenide clusters whose core at low Se content can be described as Ru2Se2O0.5. At Se:Ru = 1, high-resolution electron microscopy shows evidence of formation of core-shell particles, comprising a hexagonally packed Ru core and a Ru selenide shell with lamellar morphology. Modification of Ru nanoparticles with Se enhances their electrocatalytic activity in the oxygen reduction reaction, which is explained by the role of Se in inhibiting surface oxidation.
IMPROVEMENT OF THE PERFORMANCE OF A DIRECT METHANOL FUEL CELL USING A PULSE TECHNIQUE
M. Neergat*, T. Seiler*, E.R. Savinova, U. Stimming*
(*Technische Universität München, Garching, Germany)
J. Electrochem. Soc., 153(6) (2006) pp. A997-A1003.
A pulse method is suggested for the improvement of the performance of a direct methanol fuel cell operated with PtRu anode and Pt cathode. The pulse method can be realized either in a potentiostatic or in a galvanostatic mode. In the galvanostatic regime of low current densities it allows for a temporary hoist of the cell voltage by up to 150 mV. It is suggested that by periodically applying a pulse to the fuel cell, the anode potential is shifted to positive values at which the otherwise high COads coverage on the PtRu anode is decreased by oxidation. After the pulse, the methanol oxidation rate is enhanced until the previous COads coverage is re-established and a new pulse is then applied. Differential electrochemical mass spectroscopy data reveal that an appreciable voltage gain can be obtained at a reduction of only ca. 10–15% of the COads saturation coverage.
KINETIC MODELING OF COad MONOLAYER OXIDATION ON CARBON-SUPPORTED PLATINUM NANOPARTICLES
B. Andreaus*,**, F. Maillard***, J. Kocylo*,**, E.R. Savinova, M. Eikerling*,**
(*Simon Fraser University, Burnaby, British Columbia, Canada; **Institute for Fuel Cell Innovation, Vancouver, British Columbia, Canada; ***Laboratoire d'Electrochimie et de Physico-chimie des Matériaux et des Interfaces, Saint Martin, d'Hères, France)
J. Phys. Chem. B, 110(42) (2006) pp. 21028-21040.
A theoretical study of COad electrooxidation on Pt nanoparticles is presented. Effects of size and surface texture of nanoparticles on the interplay of relevant kinetic processes are investigated. Thereby, strong impacts of particle size on electrocatalytic activities, observed in experiments, are rationalized. Theoretical approach employs the active site concept to account for the heterogeneous surface of nanoparticles. It, moreover, incorporates finite rates of surface mobility of adsorbed CO. As demonstrated, the model generalizes established mean field or nucleation and growth models. Very good agreement of our model with chronoamperometric current transients at various particle sizes and electrode potentials was found (Maillard, F.; Savinova, E.R.; Stimming, U. J. Electroanal. Chem., in press). The full interplay of on-site reactivity at active sites and low surface mobility of COad unfolds on the smallest nanoparticles (~2 nm). In this case, the solution of the model requires kinetic Monte Carlo simulations specifically developed for this problem. For larger nanoparticles (>4 nm) the surface mobility of COad is high compared to the reaction rate constants, and the kinetic equations can be solved in the limiting case of infinite surface mobility. The analysis provides an insight into the prevailing reaction mechanisms and allows for the estimation of relevant kinetic parameters.
CO MONOLAYER OXIDATION ON Pt NANOPARTICLES: FURTHER INSIGHTS INTO THE PARTICLE SIZE EFFECTS
F. Maillard*, E.R. Savinova, U. Stimming**
(*Matériaux et des Interfaces, Saint Martin, d’Hères, France; ** Technische Universität, München, Garching, Germany)
J. Electroanal. Chem., 599(2) (2007) pp. 221-232.
This paper provides further insights into the particle size effects in CO monolayer oxidation. Strong particle size effects are confirmed in the size range from 1.8 to 5 nm. The discrepancies in the literature concerned with the particle size effects in CO monolayer oxidation are reconciled by exploring the influence of the experimental conditions on the stripping voltammograms and chronoamperograms. Evidence supporting the contribution of slow non- electrochemical step to the overall mechanism of CO oxidation is presented. The particle size effects in CO monolayer oxidation are attributed to the size- dependent COads + OHads interaction as well as to the size-dependent COads surface diffusion coefficient.
HIGH-TEMPERATURE EFFECTS ON THE ELECTRICAL PROPERTIES AND MACROSTRUCTURE OF CARBON COMPOSITES
E.I. Zhmurikov*, A.I. Romanenko**, O.B. Anikeeva**, K.V. Gubin*, E.B. Burgina, S.V. Tsybulya, A.T. Titov***, L. Tecchio****
(*Budker Institute of Nuclear Physics, Novosibirsk, Russia; **Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; ***Trofimuk Institute of Geology, Novosibirsk, Russia; ***Istituto Nazionali di Fisica Nucleare, Legnaro, Italy)
Inorg. Mater., 41(6) (2006) pp. 609-616.
The electrical conductivity of MPG-6 and MPG-7 carbon composites has been measured before and after 1.4-MeV electron irradiation and ac resistive heating up to degradation temperatures (above 2500°C). The results demonstrate that both heating and electron irradiation reduce the resistivity of the materials and increase the defect density at the macrostructural level, while X-ray diffraction analysis reveals no significant structural changes in the temperature range studied. Detailed characterization of the composites suggests that their strength is limited by crystallite or grain boundaries.
Cu(II) AND Cu(I) COMPLEXES WITH 2-(3,5-DIPHENYL-1H-PYRAZOLE-1-yl)-4,6- DIPHENYLPYRIMIDINE: SYNTHESIS AND STRUCTURE. CATALYTIC ACTIVITY OF Cu(II) COMPOUNDS IN REACTION OF ETHYLENE POLYMERIZATION
M.B. Bushuev*, V.P. Krivopalov**, N.V. Semikolenova, E.V. Peresypkina*, A.V. Virovets*, L.A. Sheludyakova*, 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., 32(3) (2006) pp. 199-207.
The Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyri- midine (L) of the composition CuLX2 (X = Cl, Br) and CuL(MeCN)Br are synthesized. According to X-ray diffraction data, the complexes have molecular structures. The molecules L are coordinated to the copper atom in bidentate-cyclic mode, i.e., through the N2 atom of pyrazole and N1 atom of pyrimidine rings. The coordination polyhedron of the Cu2+ ion in CuLX2 compounds iscompleted to a distorted tetrahedron with halide ions, that of the Cu+ ion in CuL(MeCN)Br compounds, with the bromide ion and the nitrogen atom of acetonitrile molecule. The CuLX2 complexes (X = Cl, Br) in combination with cocatalysts (methylaluminoxane and triisobutylaluminium) exhibit catalytic activity in ethylene polymerization.
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*
(*Wolfson Materials and Catalysis Centre, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, United Kingdom)
Organometal., 26(2) (2007) pp. 288-293.
Cationic intermediates formed upon activation of an 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.
DISTINCT METHYLALUMOXANE(MAO)-DERIVED Me-MAO(-) ANIONS IN CONTACT WITH A ZIRCONOCENIUM CATION - A 13C-NMR STUDY
D.E. Babushkin, C. Naundorf*, H.-H. Brintzinger*
(*Universität Konstanz, Konstanz, Germany)
Dalton Trans., 38 (2006) pp. 4539-4544.
Zirconocenium cations of the type [(MeC5H4)2ZrMe]+, formed by excess methylalumoxane (MAO) from (MeC5H4)2ZrCl2 or (MeC5H4)2ZrMe2 with 13C-labelled ring ligands, are found to form ion pairs with two types of anions, Me–MAOA– and Me–MAOB–, which differ in their coordinative strengths. More strongly coherent ion pairs [(MeC5H4)2ZrMe+ Me–MAOB–] are converted to more easily separable ion pairs [(MeC5H4)2ZrMe+ Me–MAOA ] by a sufficient excess of MAO. These react with Al2Me6 to form outer-sphere ion pairs containing the cationic AlMe3 adduct [(MeC5H4)2Zr(µ-Me)2AlMe2]+; formation of the more easily separable ion pairs might be required also for polymerisation catalysis.
FORMATION AND STRUCTURES OF CATIONIC ZIRCONIUM COMPLEXES IN TERNARY SYSTEMS rac-(SBI)ZrX2/ABui3/[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; **Wolfson Materials and Catalysis Centre, University of East Anglia, Norwich, UK)
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/AlBu3i/[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) AlBu2i] [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 AlBu3i, 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.
SUPPORTED TITANIUM-MAGNESIUM CATALYSTS WITH DIFFERENT TITANIUM CONTENT: KINETIC PECULIARITIES AT ETHYLENE HOMOPOLYMERIZATION AND COPOLYMERIZATION AND MOLECULAR WEIGHT CHARACTERISTICS OF POLYETHYLENE
L.G. Echevskaya, M.A. Matsko, T.B. Mikenas, V.E. Nikitin, V.A. Zakharov
J. Appl. Polym. Sci., 102(6) (2006) pp. 5436-5442.
The effect of Ti content on the activity of titanium-magnesium catalysts (TMC) and molecular weight distribution (MWD) of polyethylene (PE) produced has been studied. It was found that the activity enhances sharply as Ti content decreases from 0.6 to 0.07 wt %, and shows no significant changes in the Ti content range of 0.6-5.0 wt %. The maximum activity (36 kg PE/mmol Ti∙h∙bar C2H4) was observed for TMC with the lowest Ti content. The catalyst with low titanium content (~0.1 wt % of Ti) produced PE with narrower MWD (Mw/Mn = 3.1-3.5) as compared to catalysts with higher titanium content (3-5 wt % of Ti; Mw/Mn = 4.8-5.0). New data on the effect of hydrogen on MWD of PE have been found. Increasing hydrogen concentration results in broadening the MWD of PE, especially in the case of TMC with high titanium content. The data presented indicate the heterogeneity of active centers of TMC in the reaction of chain transfer with hydrogen. The data on the ethylene-hexene-1 copolymerization over TMC with different titanium content are presented. Comonomer reactivity ratios were shown to be independent of the Ti content in TMC. Presumably the difference in activity of these catalysts is mainly caused by the difference in the number of active centers.
DRIFT STUDY OF INTERNAL DONORS IN SUPPORTED ZIEGLER–NATTA CATALYSTS
A.G. Potapov, G.D. Bukatov, V.A. Zakharov
J. Mol. Catal., 246(1-2) (2006) pp. 248-254.
The state of internal donor (ID) in the supported titanium–magnesium (TiCl4/ID/MgCl2) catalysts for stereospecific propylene polymerization has been studied by diffuse reflectance infrared spectroscopy (DRIFT). The samples were prepared via interaction of highly dispersed MgCl2 with different IDs (ethyl benzoate, EB; di-n-butyl phthalate, DBP) and TiCl4. It was found that the DRIFT spectra of carbonyl groups of IDs adsorbed on MgCl2 could be best described as a superposition of several overlapping vibration bands from a variety of surface complexes. Within this model the content of individual EB and DBP complexes on the MgCl2 surface was calculated. In the case of EB, three main complexes were found on the MgCl2 support in about equal proportions. In the case of DBP, only one of three complexes was preferentially formed. The surface content of both EB and DBP was found to decrease in presence of TiCl4. At the same time TiCl4 had influenced the distribution pattern of EB but not DBP complexes. The most likely scenario of competitive adsorption of TiCl4 and IDs on the MgCl2 support is discussed. A model describing surface distribution of TiCl4 on MgCl2 is proposed for TiCl4/EB/MgCl2 and TiCl4/DBP/MgCl2 catalysts.
MOLECULAR MASS CHARACTERISTICS OF POLYETHYLENE PRODUCED WITH SUPPORTED VANADIUM-MAGNESIUM CATALYSTS
L.G. Echevskaya, M.A. Matsko, T.B. Mikenas, V.A. Zakharov
Polym. Int., 55(2) (2006) pp. 165-170.
Highly active supported vanadium-magnesium catalysts (VMC) produce polyethylene (PE) with broad and bimodal molecular mass distribution (MMD) in comparison with the famous titanium- magnesium catalysts (TMC). The effect of hydrogen as an efficient chain-transfer agent on the MMD of PE has been studied. Increasing hydrogen concentration causes a considerable broadening of MMD of PE due to the shift of the low molecular weight peak on the MMD curve. At the same time, the high molecular weight shoulder stays at the same position even at high hydrogen concentration. This means that VMC contain two types of active centre. One type is very reactive in the chain-transfer reaction with hydrogen. These centres produce low molecular weight PE in polymerization in the presence of hydrogen. The other type of active centre is not active in chain transfer with hydrogen. These centres produce high molecular weight PE ((1-3) ∙106) and hydrogen does not affect the position of the high molecular weight shoulder. MMD data were used to analyze the kinetics of the chain-transfer reaction with hydrogen and to calculate the rate constants of this reaction.
DETERMINATION OF THE MOLECULAR CHARACTERISTICS OF POLYOLEFINS WITH THE USE OF THE TOMS EFFECT
V.N. Manzhai*, L.G. Echevskaya, A.V. Ilyushnikov*, A.Z. Aisheva*, V.A. Zakharov, M.A. Matsko
(*Institute of Petroleum Chemistry, Tomsk, Russia)
J. Eng. Phys. Thermophys., 79(1) (2006) pp. 168-172.
The interrelation between the physicochemical properties of macromolecules and the hydrodynamic parameters of a turbulent flow of diluted polymer solutions in a cylindrical channel has been analytically determined. The possibility of estimating of the molecular characteristics of high-molecular polymers with the use of the turborheometric method has been considered. The antiturbulence efficiency of polyhexane used in energy-conserving technologies of pipeline transport of hydrocarbon materials has been analyzed on the basis of comparison of the molecular masses of polymers determined by different methods.
DRIFTS AND DRS STUDIES OF PHILLIPS ETHYLENE POLYMERIZATION CATALYSTS
V.N. Panchenko, V.A. Zakharov, E.A. Paukshtis
Appl. Catal., A, 313(2) (2006) pp. 130-136.
Formation of the CrO3/SiO2 catalyst prepared by the reaction of CrO3 vapor with silica pre- dehydroxylated at 250–800°C was studied by the DRIFT and DRS methods. It was found that CrO3 reacts with the silica OH-groups at 250°C to produce various chromate species and water. The latter is removed from the catalyst surface by vacuumation at 250°C. It was found the nature of CrO3 interaction with silica and the structure and composition of the surface species depend on silica dehydroxylation temperature. The reactions of CrO3 with the silica dehydroxylated at 250, 400 and 800°C yielded, respectively, monochromates; mono- and dichromates; polychromates. The catalyst activity at ethylene polymerization strongly increases with increasing dehydroxylation temperature, especially in the range of 250–400°C. The results obtained prove di- and polychromates to be the active components of the Phillips type chromium-oxide catalysts from which the active centers are formed at interaction of the active component with co-catalyst (AlEt3) and ethylene. Active centers contain the surface organo- chromium compounds with chromium ions in low oxidation states (lower than Cr(VI).
KINETIC STUDY OF ETHYLENE POLYMERIZATION OVER SUPPORTED BIS(IMINO)PYRIDINE IRON (II) CATALYSTS
A.A. Barabanov, G.D. Bukatov, V.A. Zakharov, N.V. Semikolenova, T.B. Mikenas, L.G. Echevskaya, M.A. Matsko
Macromol. Chem. Phys., 207(15) (2006) pp. 1368-1375.
The number of active centers (CP) and propagation rate constants (kP) for polymerization of ethylene with supported catalysts LFeCl2/SiO2, LFeCl2/Al2O3 and LFeCl2/MgCl2 (L = 2,6-(2,6-(Me)2C6H3N CMe)2C5H3N), activated by an Al(i-Bu)3 co-catalyst, were determined by a method of polymerization inhibition with radioactive 14CO. In contrast to homogeneous systems based on LFeCl2, the supported catalysts are highly active and stable in ethylene polymerization at 70-80°C. In the presence of hydrogen, the activity of the supported catalysts substantially increases (2-4 fold). The data obtained on the effect of hydrogen on the calculated CP and kP values suggests that for ethylene polymerization without hydrogen, the “dormant” active centers are formed in the catalytic systems. A scheme for the formation of these “dormant” centers and their reactivation in presence of hydrogen is suggested. For the investigated supported catalysts the CP values were found to be only 2 to 4% of the total iron complex content in the catalysts. The kP value for the catalysts prepared using different supports (SiO2, Al2O3 and MgCl2) were close (3.2·104 to 4.5·104 L·(mol·s)-1 at 70°C). The support composition affects neither the molecular mass (MM) nor the molecular mass distribution (MMD) of the polymers produced. The obtained CP and kP values and data on the polymer MM and MMD lead to conclusion that the nature of the support has almost no effect on the structure of the active centers and the distribution of their reactivity.
HOMOGENEOUS AND SUPPORTED CATALYSTS BASED ON BIS(IMINO)PYRIDYL IRON(II) COMPLEXES FOR ETHYLENE POLYMERIZATION
V.A. Zakharov, N.V. Semikolenova, T.B. Mikenas, A.A. Barabanov, G.D. Bukatov, L.G. Echevskaya, M.A. Matsko
Kinet. Catal., 47(2) (2006) pp. 303-309.
Data on ethylene polymerization on homogeneous and supported catalysts based on 2,6-bis(imino)pyridyl Fe(II) complexes activated by trialkylaluminums are considered (activity, the molecular-weight characteristics of polymers, the number of active sites, and the propagation rate constants). Unlike homogeneous systems, the supported catalysts prepared with the use of various carriers (SiO2, Al2O3, and MgCl2) exhibited high stability and activity at 70–80°C and produced high- molecular-weight polyethylene with a broad molecular-weight distribution (MWD). The molecular weights and MWDs of polymers and the propagation rate constant depended on the nature of the carrier only slightly. The reasons for an unusual effect of an increase in the activity of the supported catalysts in ethylene polymerization in the presence of hydrogen are discussed.
NEW REACTION FOR PREPARATION OF LIQUID RUBBER
K.A. Dubkov, S.V. Semikolenov, D.E. Babushkin, L.G. Echevskaya, M.A. Matsko, D.P. Ivanov, V.A. Zakharov, V.N. Parmon, G.I. Panov
J. Polym. Sci., Part A: Polym. Chem., 44(8) (2006) pp. 2510-2520.
The article reports on the noncatalytic transformation of a polybutadiene (number-average molecular weight = 128,000) into a functionalized liquid rubber via the carboxidation of the polymer C=C bonds by nitrous oxide. The reaction was conducted in a benzene solution at 160-230°C and a pressure of 3-6 MPa. The carboxidation mechanism was determined. The main route (95%) of the reaction proceeded without cleavage of C=C bonds and led to the formation of ketone groups in the polymer backbone. A minor route (5%) of the reaction proceeded with the cleavage of C=C bonds, yielding two smaller fragments containing aldehyde and vinyl end groups. The availability of the cleavage route could lead to a dramatic decrease in the molecular weight, which, depending on the carboxidation degree, could be 1-2 orders of magnitude less than that of the initial material. Thus, the carboxidation of more than 15% of the polybutadiene C=C bonds transformed it into a C=O-functionalized liquid rubber with a narrow molecular weight distribution.
POLYMERIZATION OF ETHYLENE BY SiO2-SUPPORTED TWO-COMPONENT CATALYTIC SYSTEMS CONTAINING BIS(IMINO)PYRIDINE AND BIS(IMINE) LIGANDS
S.S. Ivanchev, N.I. Ivancheva, S.Ya. Khaikin, E.V. Sviridova, D.G. Rogozin
Polymer Sci., Ser A, 48(3) (2006) pp. 251-256.
The polymerization of ethylene initiated by SiO2-supported two-component catalytic systems based on 2,6-bis[1-(2,4-dimethyl-6- cyclohexylphenylimino)ethyl]pyridine iron (II) chloride (I) and 1,2-bis(2-cyclohexyl-4,6- dimethylphenylimino)acenaphthene] nickel bromide (II) was studied. Methylaluminoxane was used as a cocatalyst during support. It was shown that the activity of two-component catalytic systems and the molecular mass and short-chain branching of polyethylene samples depend on the supporting procedure: simultaneous immobilization of components I and II, separate immobilization of components on the support (first I, then II, and vice versa), and the use of a mixture of components I and II immobilized separately on SiO2.
NANOSTRUCTURES IN POLYMER SYSTEMS
S.S. Ivanchev, A.N. Ozerin*
(*Enikolopov Institute of Synthetic Polymer Materials, Moscow, Russia)
Polymer Sci., Ser B, 48(7-8) (2006) pp. 213-225.
General concepts concerning the formation, structure, and some properties of nanosized structural elements in polymers and polymeric materials are summarized from the standpoint of feasibility of formation of nanoparticles and nanoreactors in such systems and practical use of advantages offered by these structures. The familiar concepts are complemented with the results obtained recently. Examples are given to illustrate the implementation of elements of nanotechnology based on the principles of creation of nanostructures in amorphous and crystalline polymers, copolymers, and molecular composites. Practicable methods for the preparation of polymeric nanostructures by controlled crystallization, microphase and nanophase separation of components, and their dispersion, as well as the formation of interfaces, are discussed.
TRANSETHERIFICATION OF MELAMINE- FORMALDEHYDE RESIN METHYL ETHERS AND COMPETING REACTION OF SELF-CONDENSATION
V.N. Pavlyuchenko, S.S. Ivanchev, M. Rätzsh*, H. Bucka*, O.N. Primachenko, P. Leitner*, S.Ya. Khaikin
(*AMG Agrolinz Melamine International GmbH, Linz, Austria)
J. Appl. Polym. Sci., 110(5) (2006) pp. 2977-2985.
Transetherification of methyl ethers of melamine- formaldehyde resin (MER) with monophenyl ethers of ethylene glycol or propylene glycol (ROH) and competing reaction of self-condensation are studied depending on MER composition (amounts of CH3O-, -CH2OH, and NH2-groups, ROH type, MER/ROH molar ratio), presence or absence of acid catalysts, and temperature. High rates of self-condesation processes prevent a complete conversion of CH3O-into RO-groups. It turned out MER free of methylol groups were not able to be transetherified with high yields due to a premature gelation taking place prior to attaining 50% conversion of methoxy groups (~ 4 mol/kg) even at low MER/ROH ratios. In contrast, transetherification of MER with methylol groups content up to 3 mol/kg affords the incorporation of RO-groups into the resin up to 8 mol/kg owing to direct etherification of –CH2OH groups. The following factors are responsible for the growth of etherified product yield: presence of methylol groups in MER in some amounts without deterioration of MER-ROH compatibilization; CH3O-/ROH molar ratio no higher than 1; primary alcohols (ROH) is more preferable compared to secondary ones; thermal activation of the process is more efficient in comparison with acidic catalysis.
POLYMER HYDROGELS BASED ON 2-HYDROXYETHYL METHACRYLATE: MODIFICATION, SORPTION, AND DESORPTION OF AMINOGLYCOSIDES
V.N. Pavlyuchenko, N.A. Ushakov*, S.A. Novikov*, V.F. Danilichev*, V.A. Reituzov*, S.S. Ivanchev
(*Kirov Military Medicine Academy, St. Petersburg, Russia)
Russ. J. Appl. Chem., 79(4) (2006) pp. 584-589.
Methods of modification of polymer hydrogels based on 2-hydroxyethyl methacrylate with the aim to improve their hydrophilic characteristics are described. The absorption of antibiotics such as aminoglycosides and the kinetics of their liberation from modified hydrogels are studied.
NEW METHODS FOR PRODUCTION OF THERAPEUTIC SOFT CONTACT LENSES
V.F. Danilichev*, S.S. Ivanchev, N.A. Ushakov*, V.N. Pavlyuchenko, V.A. Reituzov*, A.S. Bobasheva
(*Military Medical Academy, St. Petersburg, Russia)
In: “Ophthalmology of the Black Sea Region”, Krasnodar, 2006, pp. 352-355.
New polymer hydrogel material is synthesized and methods for production of soft contact lenses (SCL) is developed. 1. The developed silicon-hydrogel medical soft contact lenses (MSCL) possess high oxygen permeability (Dk/t > 125) and can be applied for effective relief of the corneal syndrome. 2. MSCL are developed based on synthetic polymer hydrogels with a high water content (70-94.5 wt %). They feature an enhanced sorbability for medical products and capability of releasing them at a controlled rate. 3. The developed biopolymer (gelatin) based MSCL with water content of 80–90 wt % demonstrate a high biological activity and are applicable as wound healing agents in cases of eye damage or diseases.
MEDICAL SOFT CONTACT LENSES BASED ON POLYMER HYDROGELS
V.F. Danilichev*, S.S. Ivanchev, N.A. Ushakov*, V.N. Pavlyuchenko, V.A. Reituzov*, A.S. Bobasheva, E.V. Muravieva*
(*Military Medical Academy, St. Petersburg, Russia) The Eye, 5 (2006).
Under discussion is the therapeutic effect of new soft contact lenses (MSCL) synthesized on the basis of polymer hydrogels with high water content (polyacrylamide, cross-linked gelatin, alkali-modified poly-2-hydroxyethylmetacrylate), as well as a new highly oxygen-permeable silicon-hydrogel. The new MSCL are demonstrated to be effective bandage to relief the corneal syndrome and to accelerate reparative processes on treating endothelial and epithelial dystrophia and postoperative complications. In order to estimate the MSCL efficiency, several factors are proposed to consider simultaneously; these factors are sorbability of the polymer hydrogel with respect to an antibiotic, antibacterial activity of the antibiotic, the antibiotic capability of crossing the hemoophthalmic barrier. Optimal hydrogel-antibiotic combinations are identified.
QUANTUM-CHEMICAL STUDIES OF THE STRUCTURE AND CATALYTIC ACTIVITY OF BIS(PHENOXYIMMINE) COMPLEXES OF TITANIUM AND ZIRCONIUM
A.V. Yakimanskii, S.S. Ivanchev
Doklady Chem., 410(2) (2006) pp. 217-219.
Quantum chemical calculations were performed to establish regularities of the influence of structures of bis(phenoxyimmine) complexes of titanium and zirconium on the process energy during the formation of catalytically active species and their complexes with ethylene, growth of the polymer chains, as well as on the energy of concurrent catalyst deactivation and decomposition processes.
ELECTRON RADIATION EFFECTS ON THE STRUCTURE OF ULTRADISPERSE POLYTETRAFLUOROETHYLENE
>L.N. Ignatieva*, V.G. Kuryavyi*, T.A. Kaidalova*, V.M. Bouznik, A.I. Korchagin**
(*Institute of Chemistry, Vladivostok Russia; **Budker Institute of Nuclear Physics, Novosibirsk, Russia)
J. Struct. Chem, 46(5) (2005) рр. 848-855.
Electron radiation effects (40 mrad, 70 mrad, and 100 mrad) on the molecular and supramolecular structure and morphology of ultradisperse polytetrafluoroethylene obtained by the thermogas dynamic (TGD) method were studied by IR and EPR spectroscopy, X-ray phase analysis, and atomic force microscopy. Irradiation of ultradisperse powder in air leads to oxidized polymer forms due to the terminal carbonyl groups and stable peroxide radicals that appear in the structure. Fast electron radiation in doses of up to 100 mrad did not change the polymer crystallinity and particle entity, while thin films on the surface of ultradisperse polytetrafluoroethylene powder decomposed.
OPTICAL ISOTROPIC MESOPHASE IN SIDE CHAIN COPOLYMERS CONTAINING ISOPHTHALIC ACID GROUPS
E.B. Barmatov*, D.A. Pebalk**, M.V. Barmatova
(*Schlumberger Novosibirsk Technol Ctr, Novosibirsk, Russia; **Moscow Lomonosov State University, Moscow, Russia)
Liq. Cryst., 33(5) (2006) pp. 621-624.
Random side chain copolymers, containing cyanobiphenyl mesogenic units and 37-58 mol% of isophthalic acid monomer units, possess an unusual ability to produce optically isotropic mesophases. This is demonstrated by the absence of birefringence and by high optical transparency of their films. At the same time, corresponding DSC curves show a well pronounced first order transition with a heat of fusion of 1.5-2.34 kJ mol-1. A key reason behind the formation of an optically isotropic mesophase is likely to be related to the microphase separation between side groups of the copolymers.
INFLUENCE OF SILVER NANOPARTICLES ON THE ORDER PARAMETER OF LIQUID CRYSTALLINE POLYMERS
E.B. Barmatov*, D.A. Pebalk**, M.V. Barmatova
(*Schlumberger Novosibirsk Technol Ctr, Novosibirsk, Russia; **Moscow Lomonosov State University, Moscow, Russia)
Liq. Cryst., 33(9) (2006) pp. 1059-1063.
New polymer nematic nanocomposites are prepared containing 1.43-4.64 wt% of silver nanoparticles whose mean dimensions are 2-4 nm. According to H2 NMR spectroscopic measurements, on increasing the content of metallic nanoparticles, the orientational order parameter S-zz of the nematic phase shown by the nanocomposites increases.
NEW COMPOSITE ADSORBENTS FOR CONVERSION AND STORAGE OF LOW TEMPERATURE HEAT: ACTIVITY IN THE BORESKOV INSTITUTE OF CATALYSIS
Yu.I. Aristov
J. Heat Transfer Soc. Jpn., 45(192) 2006) pp. 12-19.
In this communication it is discussed how to design new solid sorbents with sorption properties close or even equal to those perfectly fitting the cycle. In the first part the mentioned requirements are formulated for a particular single-effect non- regenerative cycle driven by low temperature heat. The conclusion has been made that solid sorbents which match in the best way the theoretical requirements for mentioned cycle are those with a monovariant equilibrium, specifically, salts and their crystalline hydrates capable of exchanging water due to chemical reaction with the salt. The second part of the paper is devoted to practical tools, which are available to design and synthesise an optimal composite sorbent of water for a particular ATH cycle. It was proved that the sorption properties of SWSs can be monitored by a proper choice of the chemical nature and content of the confined salt, the average size of pores of the host matrix and synthesis conditions. Thus, this part reviews the current state-of- the art on the new family of the SWS composites.
A NEW APPROACH TO HEAT AND MOISTURE REGENERATION IN THE VENTILATION SYSTEM OF ROOMS. I. LABORATORY PROTOTYPE OF THE REGENERATOR
Yu.I. Aristov, I.V. Mezentsev*, V.A. Mukhin**
(*Institute of Thermal Physics, Novosibirsk, Russia; **Siberian University of Communications, Novosibirsk, Russia)
J. Engin. Phys. Thermophys., 79(3) (2006) pp. 569-576.
A new heat-and-mass transfer device that a) permits simultaneous heat and moisture regeneration in the ventilation system, b) provides anti-icing at the heat-exchanger outlet, and c) maintains comfortable humidity in a room is proposed. In this unit a composite sorbent is used for moisture exchange and a heat accumulating medium for heat exchange between income and outcome air fluxes. First part presents experimental results on cyclic heat exchange and its optimization to reach a high degree of heat regeneration. Proper heat storing material and its grain size were chosen. The affect of the air residence time and half cycle time on regeneration degree was studied.
A NEW APPROACH TO HEAT AND MOISTURE REGENERATION IN THE VENTILATION SYSTEM OF ROOMS. II. PROTOTYPE OF THE REAL DEVICE
Yu.I. Aristov, I.V. Mezentsev*, V.A. Mukhin**
(*Institute of Thermal Physics, Novosibirsk, Russia; **Siberian University of Communications, Novosibirsk, Russia)
J. Engin. Phys. Thermophys., 79(3) (2006) pp. 577-584.
This paper presents the results of investigations conducted on the real prototype of a regenerator whose operating conditions depended on the weather conditions during the testing (winter of 2004). It has been shown that the heat and moisture recovery coefficients can be purposefully and independently regulated in a wide range by proper adsorbent and heat-accumulating medium selection. The use of the proposed device in the ventilation system of a standard two-room apartment can lead to a 44% reduction of heating costs annually.
KINETICS OF WATER ADSORPTION ON SILICA FUJI DAVISION RD
Yu.I. Aristov, M.M. Tokarev, A. Freni*, I.S. Glaznev, G. Restuccia*
(*CNR – Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano”, Messina, Italy)
Microporous Mesoporous Mater., 96(1-3) (2006) pp. 65-71.
The kinetics of water adsorption on loose grains of Fuji Davison RD silica gel was studied by a TG differential step method in the temperature range 29–64°C and in the pressure range 6.5–34 mbar. Three grain sizes were selected, 0.3–0.325, 0.355–0.425 mm and 0.8–1.0 mm. Furthermore, adsorption isobars at PH2O = 9, 18 and 48 mbar were measured over the temperature range of 30–150°C by a TG technique to determine pertinent equilibrium parameters which are used to calculate the coefficients of diffusion. The equilibrium uptake was described as a linear function of the Dubinin–Polanyi adsorption potential. It was found that the influence of particle size, temperature and pressure on the adsorption kinetics can be well described in terms of the Fickian diffusion model. The apparent water diffusivity Dap was found to be an Arrhenius function of temperature with the apparent activation energy Ea = 41.5 kJ/mol and the pre-exponential factor Dap0 = 2.9 × 10−4 m2/s. The apparent diffusivity of water in silica pores was measured to be De = (3.7–4.7) × 10−7 m2/s and possessed a slight increase with temperature. This value is close to the Knudsen diffusivity, calculated for a cylindrical pore of radius rp = 1.0 nm. For smaller grains at T > 39°C the contribution of thermal effects was revealed, which decreases the rate of water sorption. In this case, application of non- isothermal kinetic model of Lee and Ruthven allowed good description of experimental uptake curves as well as the estimation of parameters which determine simultaneous heat and mass transfer.
KINETICS OF WATER SORPTION ON SWS-1L (CALCIUM CHLORIDE CONFINED TO MESOPOROUS SILICA GEL): INFLUENCE OF GRAIN SIZE AND TEMPERATURE
Yu.I. Aristov, I.S. Glaznev, A. Freni*, G. Restuccia*
(*CNR – Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano”, Messina, Italy)
Chem. Eng. Sci., 61(5) (2006) pp. 1453-1458.
Kinetics of water sorption on loose grains of composite sorbent CaCl2 confined to mesoporous silica (SWS-1L) was measured at T=33-69°C and P(H2O)=8-70 mbar over water uptake range 0–0.47 g/g for various particle sizes Rp (between 0.355 and 1.4 mm). The measurements were performed in a constant pressure unit based on a CAHN microbalance under isothermal external conditions. The results obtained evidence an enhancement of the sorption rate and apparent diffusion constant with the decrease in the particle size (approximately as Rp-2 at Rp > 0.71 mm). Contribution of thermal effects was found for water sorption on smaller SWS particles (0.355–0.425 mm), which decreases the sorption rate. The apparent water diffusivity was found to depend on the local slope of the SWS water sorption isotherm. The pore diffusivity of water in the temperature range 33-69°C was calculated from experimental data De = (0.12 ± 0.06)×10-6 m2/s that is approximately 10 times lower than the Knudsen pore diffusivity estimated for pores of silica KSK. The possible reasons of the diffusivity reduction are discussed.
KINETICS OF WATER SORPTION ON A CaCl2-IN-SILICA-GEL-PORES SORBENT: THE EFFECTS OF THE PELLET SIZE AND TEMPERATURE
Yu.I. Aristov, I.S. Glaznev, A. Freni*, G. Restuccia*
(*CNR—Instituto di Tecnologie Avanzate per l’Energia “Nicola Giordano”, Messina, Italy)
Kinet. Catal., 47(5) (2006) pp. 770-775.
Kinetics of water vapor sorption on the CaCl2-in- KSK-pores composite (SWS-1L) have been studied at T = 33-69°C and vapor pressures of 8–70 mbar for pellet sizes of 2Rpel = 0.355–0.425, 0.71–0.85, and 1.2–1.4 mm. Sorption has been measured under isothermal conditions on a thermobalance by abruptly raising the vapor pressure in the measurement cell by a small value and then maintaining the new pressure. In the initial portion of the kinetic curves, the amount of sorbed water (Δm) increases in proportion to the sorption time (t) to the power 1/2. From the slope of the Δm versus t1/2 curve, it is possible to derive the sorption rate constant kD = Deff/Rpel and the effective diffusivity Deff. The latter is independent of Rpel for 2Rpel ≥ 0.71 mm. The rate of water sorption on smaller (0.355-0.425 mm) pellets grows less rapidly, apparently because of the effect of the heat of sorption. The effective diffusivity is determined by the local slope of the water vapor sorption isotherm for SWS-1L. Applying an appropriate correction enables one to calculate the effective diffusivity for water vapor in the sorbent pores, which appears to be De=(0.35±0.17)∙10-6 m2/s. This value is approximately 10 times smaller than the Knudsen water diffusion coefficient calculated for a single cylindrical pore with a size equal to the average pore size of the composite. Two possible causes of this discrepancy are discussed, specifically, an increase in the pore tortuosity because of the presence of the salt and the interaction between water and the salt.
DYNAMICS OF HYDRATION WATER IN CaCl2 COMPLEXES
M. Plazanet*, I.S. Glaznev, A.G. Stepanov, Yu.I. Aristov, H. Jobic**
(*Institute Laue Langevin, Grenoble, France; **Institut de Recherches sur la Catalyse, Villeurbanne, France)
Chem. Phys. Lett., 419(1-3) (2006) pp. 111-114.
The measurement of unusually well-defined vibrational modes of water are reported. Calcium chloride forms complexes made of different amounts of water, namely 1/3, 2 or 4 water per CaCl2 molecule. Based on the crystallographic structure, normal mode calculations from first principles were performed, and the neutron scattering spectra were simulated. A very good agreement between calculation and experiment, without any parameter refinement, confirms and completes the intuitive assignment of vibrational excitations of water. A closer look at the calculation enables to investigate the anharmonicity of the system and the dispersion of the excitations along the hydrogen bonds.
DYNAMICS OF WATER VAPOR SORPTION IN A CaCl2/SILICA GEL/BINDER BED: THE EFFECT OF THE BED PORE STRUCTURE
Yu.I. Aristov, I.V. Koptyug*, L.G. Gordeeva, L.Yu. Il’ina*, I.S. Glaznev
(*International Tomography Center, Novosibirsk, Russia)
Kinet. Catal., 47(5) (2006) pp. 776-781.
The dynamics of water vapor sorption in a compact, binder-containing bed of a CaCl2-in-silica- gel-pores sorbent has been investigated by NMR microscopy. The procedure suggested for the preparation of this bed allows the porous structure of the bed to be modified in a wide range. The bed pore structure and water transfer in the bed have been studied in relation to the particle size of the initial silica gel, the size of mesopores in the sorbent particles, and the binder content. By varying these parameters, it is possible to optimize the ratio of the diffusion resistance of the interparticle macropores to that of the internal mesopores of the particles. If sorption is controlled by water diffusion in the macropores, a sorption front forms in the sample to move inside the bed. The distance traveled by the front is proportional to the sorption time to the power 1/2. The effective diffusion coefficient of water in the macropores is estimated from the front motion dynamics to be between 0.8 10–9 and 3.0 10–9 m2/s, depending on the porous structure of the bed.
DYNAMICS OF WATER SORPTION ON COMPOSITES “CaCl2 IN SILICA”: SINGLE GRAIN, GRANULATED BED, CONSOLIDATED LAYER
Yu.I. Aristov, I.S. Glaznev, L.G. Gordeeva, I.V. Koptyug*, L.Yu. Ilyina*, J. Kärger**, C. Krause**, B. Dawoud***
(*International Tomographic Center, Novosibirsk, Russia; **University of Leipzig, Leipzig, Germany; ***RWTH-Aachen, Germany)
Fluid Transport in Nanoporous Materials: Proceedings of the NATO Advanced Study Institute, NATO Science Series II: Mathematics, Physics and Chemistry, Springer, Eds. W.C. Conner, J. Fraissard, 2006, pp. 553-565.
In the paper results on kinetics of water sorption on composite “CaCl2 in mesoporous silica KSK” are presented. Three adsorbent configurations are considered, namely, a single grain, a granulated layer and a consolidated layer prepared with a binder and pore-forming additives. Three methods have been used to study the water transport and sorption: a) 1H NMR microimaging experiments on the spatial distribution of sorbed water in the sorbent and its temporal evolution, b) the PFG NMR method and c) the kinetics of water sorption under constant volume-variable pressure conditions.
IMPACT OF PHASE COMPOSITION ON WATER ADSORPTION ON INORGANIC HYBRIDS “SALT/SILICA”
L.G. Gordeeva, I.S. Glaznev, E.V. Savchenko*, V.V. Malakhov, Yu.I. Aristov
(*Novosibirsk State University, Novosibirsk, Russia)
J. Colloid Interface Sci., 301(2) (2006) pp. 685-691.
The effect of a “guest–host” interaction on the phase composition and sorption properties of the composite sorbents “salt in a porous host matrix” has been studied. The matrix was a mesoporous silica of KSK type, while the confined salts were CaCl2, CuSO4, MgSO4, and Na2SO4. Both structure and properties of the composites were studied by X-ray diffraction, titration in the pH range of 2–9, differential dissolution, and TG techniques. Chemical interaction between the silica surface and the salt during preparation results in the formation of the salt surface complexes and stabilization of the dispersed salt in two phases, namely, a crystalline phase and an X-ray amorphous phase. The water sorption properties of the composites depend on the phase composition and can be intently modified by using variation of the preparation conditions.
AMMONIA SORPTION ON COMPOSITES "CaCl2 IN INORGANIC HOST MATRIX": ISOSTERIC CHART AND ITS PERFORMANCE
V.E. Sharonov, J.V. Veselovskaya, Yu.I. Aristov
Int. J. Low Carbon Techn., 1(3) (2006) pp. 191-200.
The isosteres of ammonia sorption on new composite sorbents “CaCl2/γ-Al2O3” and “CaCl2/vermiculite” were measured at T = 20-90°C and P = 0.08-9 bar. It was found that the modification of host matrices by the salt dramatically increases the ammonia uptake due to the formation of CaCl2×nNH3 complexes. The isobaric enthalpy and entropy of ammonia sorption by the salt confined to alumina pores were significantly lower respect to those for the bulk one. For a basic cycle, the values of COP = 0.40-0.48 were calculated at Te = –18°C, Tc = 36-42°C and Tg = 117-120°C. High COP could make these sorbents promising for application in cooling units driven by relatively low temperature heat.
ASSESSMENT OF THE OPERATION OF A LOW-TEMPERATURE ADSORPTION REFRIGERATOR
D.M. Chalaev*, Yu.I. Aristov
(*Institute of Engineering Thermal Physics, Kiev, Ukraine)
Therm. Eng., 53(3) (2006) pp. 240-244.
A simple algorithm is proposed, based on Polanyi’s temperature invariance principle, for selecting adsorbents that hold promise for the development of adsorption refrigerators using sources of low-grade heat (industrial heat wastes, solar energy, etc.). It is shown that, among the materials considered, those holding most promise for the development of adsorption systems for cooling water are new composite selective water sorbents, primarily KSKG silicagel modified with calcium chloride.
NEW COMPOSITE WATER AND AMMONIA SORBENTS FOR CHEMICAL AND ADSORPTION HEAT PUMPS
Yu.I. Aristov, L.L. Vasiliev*
(*A.V. Luikov Heat and Mass Transfer Institute, Minsk, Belarus)
J. Engin. Phys. Thermophys., 79(6) (2006) pp. 531-552.
Review of new composite water and ammonia sorbents - composites “salt in a porous host matrix” is given. Possibility of monitoring sorption properties of composites on the nanophase level by proper choice of their composition, size of pores of the host matrix and synthesis conditions is shown. The use of new materials in devices for storage of low temperature heat is considered.
COPPER AND SILVER ACTIVITY IN THE COURSE OF PARTIAL ETHYLENE GLYCOL OXIDATION
A.S. Knyazev*, V.S. Shmotin*, A.A. Magaeva*, A.I. Boronin, A.N. Salanov, O.V. Vodyankina*, L.N. Kurina*
(*Tomsk State University, Tomsk, Russia)
Catal. Ind., 5 (2006) pp. 25-30.
The partial ethylene glycol oxidation allows producing glyoxal – valuable product used in a number of organic syntheses. The process is not realized commercially in Russia that is caused by the lacking of proper domestic catalytic systems. Activities of polycrystalline Cu- and Ag-catalysts for the ethylene glycol oxidation process proposed for production are compared. Copper and silver activities are studied under the comparable conditions with variation of temperature and oxygen content in the reaction mixture. A possibility was shown to improve the given value for both metals by introducing phosphor-containing promoters to facilitate the formation of dispersed metal particles on the surface, which act as highly active centers of ethylene glycol to glyoxal conversion. The catalysts studied may be recommended to be used as active systems of industrial synthesis of glyoxal.
LIQUID PRODUCTS OF THE PROCESSES OF HYDROGENATION AND HYDROPYROLYSIS OF BARZAS SAPROMIXITE
V.I. Sharypov*, B.N. Kuznetsov*, N.G. Beregovtsova*, N.Yu. Vasil’eva**, V.A. Sokolenko*, N.I. Pavlenko*, A.N. Startsev, V.N. Parmon
(*Institute of Chemistry and Chemical Technology, Krasnoyarsk, Russia; **Krasnoyarsk State University, Krasnoyarsk, Russia)
Chem. Sustain. Devel., 14(1) (2006) pp. 73-80.
Liquid products of the processes of hydrogenation and hydropyrolysis of Barzas sapromixite under autoclave conditions are studied. The application of mechanochemically activated iron-ore catalyst in the processes of hydrogenation and hydropyrolysis of sapromixite allows one to increase the content of distillate fractions in liquid products, and low- molecular hydrocarbons in low-boiling fraction with boiling point 180°C.
CATALYTIC HYDROLIQUEFACTION OF BARZASS LIPTOBIOLITIC COAL IN A PETROLEUM RESIDUE AS A SOLVENT
V.I. Sharypov*, B.N. Kuznetsov*, N.G. Beregovtseva*, A.N. Startsev, V.N. Parmon
(*Institute of Chemistry and Chemical Technology, Krasnoyarsk, Russia)
Fuel, 85(7-8) (2006) pp. 918-922.
Hydrogenation of liptobiolitic coal from the Barzas Pit (Russia) in a petroleum residue as a solvent was investigated in the presence of an iron containing ore catalyst at 400-430°C and working pressure 7.1 MPa. Near 94-97% of the coal organic mass was converted into gaseous and liquid products. The addition of the catalyst in amount of 5% to the coal mass increases the degree of the coal conversion by 21-23 wt%. Under these conditions, the yield of hydrocarbon light liquid products (bp<200°C) was increased up to 24-28 wt%. The distillate products consist mainly of paraffins, while most part of the aromatic hydrocarbons are alkylbenzenes.
SYNTHESIS OF METHYLMERCAPTAN FROM METHANOL AND HYDROGEN SULFIDE AT ELEVATED PRESSURE ON AN INDUSTRIAL CATALYST
A.V. Mashkina
Petr. Chem., 46(1) (2006) рр. 28-33.
The catalytic reaction of methanol with hydrogen sulfide at a total pressure of 0.1–1.8 MPa was investigated. The main product at different values of total pressure in the system was methylmercaptan, and the by-products were dimethyl sulfide, dimethyl ether, carbon oxides. An increase in the contact time increased the yields of methylmercaptan and dimethyl sulfide, whereas the yields of dimethyl ether and gases changed slightly. The selectivity for methylmercaptan was approximately constant up to a ~95% conversion of methanol. The elevation in temperature increased the reaction rate but barely affected the product formation selectivity. The rate of methanol conversion increases linearly with the hydrogen sulfide concentration and depends on the methanol concentration raised to a power of 0.4–0.5; water retards the process. The selectivity for methylmercaptan decreases, and that for dimethyl sulfide and dimethyl ether increases at an H2S to methanol molar ratio below 1.4 : 1, regardless of thevalue of total pressure. The reaction rate increases with the total pressure raise to a power 0.4–0.5; however, the selectivities for methylmercaptan and by-products remain unchanged.
METHANE OXIDATION BY LATTICE OXYGEN OF CeNbO4+d
A.A. Yaremchenko*, V.V. Kharton*, S.A. Veniaminov, V.D. Belyaev, V.A. Sobyanin, F.M.B. Marques*
(*Department of Ceramics and Glass Engineering, 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.
CATALYSTS FOR NON-OXIDATIVE METHANE CONVERSION
A.V. Vosmerikov*, V.I. Zaikovskii, L.L. Korobitsyna*, Y.G. Kodenev, V.V. Kozlov*, G.V. Echevsky
(*Institute of Petroleum Chemistry, Tomsk, Russia)
Stud. Surf. Sci. Catal., 162 (2006) pp. 913-920.
In the last few years the researchers give considerable attention to the process of the Non-Oxidative Methane Conversion into aromatic hydrocarbons over zeolite catalysts modified by the ions of transient metals. Generally, the catalysts are produced via mechanical mixing of a zeolite with metal oxide or via zeolite impregnation by metal salt solution followed by drying and calcination. The present paper cites the data on the production of Mo-containing catalysts of methane dehydroaromatization both by conventional methods and using a nanosized powder (NSP) of molybdenum (0.5-6.0 wt%) produced via wire electroexplosion in argon medium. The tests of the catalytic activity of Mo/ZSM-5 catalysts produced were performed in a flow type installation at 750°C, gas hourly space velocity 1000 h-1 and atmospheric pressure. The methods of high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) spectroscopy were used to study the state of active sites of the catalysts produced. In accordance with the data of HRTEM and EDX analysis, Mo is present in the catalysts in two forms. The first Mo form is stabilized on the zeolite surface as the 2-10 nm particles and identified as a phase of Mo2C carbide. In the inner zeolite channels the second form of Mo stabilization as Mo-containing clusters less than 1 nm was found. The increase in the Mo content in a zeolite to 6 wt% results in the increase in the size of intravolume clusters to ~ 2 nm. Using HRTEM, it was established that during the preparation and reaction two kinds of mesopores are formed in the porous zeolite texture: extended mesopores 3-10 nm in diameter having the exit to the external surface and mesopores formed as a result of zeolite dealumination in the reaction course followed by the formation of Mo aluminates or its carbided forms. The development of the mesoporous zeolite structure is an important factor promoting the activity of Mo-HZSM in the reactions of the formation of high-molecular aromatic compounds. A higher activity and stability of the catalysts produced using Mo NSP as compared with other samples were established.
METHANOL DEHYDROGENATION OVER COPPER-CONTAINING CATALYSTS MODIFIED BY ZINC OXIDE
A.A. Vedyagin, P.G. Tsyrulnikov*, N.O. Struikhina*, T.A. Dashuk*, A.V. Bubnov*
(*Institute of Hydrocarbons Processing, Omsk, Russia)
Catal. Ind., 3 (2006) pp. 29-33.
The aim of the work is improvement of catalytic properties of copper-containing methanol-to-methyl formate dehydrogenation catalysts, methyl formate being industrially important semiproduct in the organic synthesis processes. The effect of modifying zinc oxide additive on activity and selectivity to methyl formate of 5%Cu/SiO2 and 5%Cu/Sibunit catalysts was investigated. It was found that its introduction results in increasing the yield of methyl formate up to 1,2–1,5 times for silica gel-based samples but the opposite dependence for Sibunit- based one. The X-ray phase analysis was used to study the nature of observed differences: it was found the dispersion of copper particles in the case of SiO2 and their coarsening in the case of Sibunit using. The modified catalyst with Cu/ZnO = 2/1 ratio may be recommended for operation at the semi-industrial scale.
DIMERIZATION OF α-METHYLSTYRENE ON HIGH-SILICA ZEOLITES
N.G. Grigor’eva*, R.R. Galyautdinova*, E.A. Paukshtis, B.I. Kutepov*, M.I. Tselyutina*, U.M. Dzhemilev*
(*Institute of Petroleum Chemistry and Catalysis, Ufa, Bashkortostan, Russia)
Petrol. Chem., 46(5) (2006) pp. 332-337.
α-Methylstyrene dimerization was studied on high-silica β, ZSM-12, and TsVN zeolites. The acid properties of the zeolites were studied by IR spectroscopy. It was revealed that the catalytic properties of the zeolites in α-methylstyrene dimerization depend on both the acidic and structural characteristics of the catalysts. The highest activity in the reaction was exhibited by zeolite β, as the maximum amount of acid sites were found in its structural units (inside channels, on the outer surface). Zeolite ZSM-12 had the highest selectivity for linear dimers.
ZrFe INTERMETALLIDES FOR FISCHER-TROPSCH SYNTHESIS: PURE AND ENCAPSULATED INTO ALUMINA-CONTAINING MATRICES
S.F. Tikhov, A.E. Kuz'min*, 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
(*Institute of Petrochemical Synthesis, Moscow, Russia)
Stud. Surf. Sci. Catal., 163 (2006) pp. 125-128.
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 300ºC, 3 MPa and space velocity ~7000 h-1.
HYDROGENATION OF SOME NATURAL TERPENES OVER СuО-Al2O3 AND NiО-Cr2О3 CATALYSTS
S.S. Laev*, V.V. Fomenko*, T.M. Yurieva, T.P. Minyukova, N.F. Salakhutdinov*
(*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia)
Chem. Sustain. Devel., 14(5) (2006) pp. 523-528.
Reaction of catalytic hydrogenation of natural compounds (limonene, α-pinene, β-pinene, camphene, 3-carene) is studied over СuО-Al2O3, NiО-Cr2О3 and for comparison over Pt/γ-Al2O3 catalysts at high temperatures (180-350оС) and under the pressure 2.5-3 atm in catalytic flow reactor. Reaction products were analyzed by chromatomass spectrometry quantitatively and qualitatively. The highest efficiency and high selectivity were observed on СuО-Al2O3 catalyst. Isomeric mixture of para-mentanes, or para-1-menten is formed from limonene depending on catalyst activity; α- and β-pinenes gives a mixture of cis- and trans-pinanes with prevalence of the last isomer; camphene gives isomeric mixture of exo- and endo-isocamphenes in equal quantities; 3-carene gives 1,1,4-trimethylcycloheptane.
EFFECT OF OXYGEN MOBILITY IN SOLID CATALYST ON TRANSIENT REGIMES OF CATALYTIC REACTION OF METHANE PARTIAL OXIDATION AT SHORT CONTACT TIMES
S.I. Reshetnikov, A.I. Lukashevich, G.M. Alikina, V.A. Sadykov
Catal. Lett., 110(3-4)(2006) pp. 235-242.
Mathematical modeling of the effect of the oxygen mobility in a solid oxide catalyst on the dynamics of transients of fast catalytic reactions has been carried out. The analysis was based upon the redox mechanistic scheme with a due regard for diffusion of oxygen from the bulk of catalyst to its surface. Parameters of kinetic and mathematical models were selected via fitting of the experimental data for methane selective oxidation into syngas on 1.4%Pt/Gd0.2Ce0.4Zr0.4Ox catalyst. The range of the Thiele parameter (φ) where the oxygen bulk diffusion affects the most strongly reaction transients corresponds to φε [0.3÷7]. For high-surface-area oxide catalysts, the bulk oxygen diffusion coefficients corresponding to this range of the Thiele parameter are in the range of 10–18÷10–13cm2/s.
EXPERIMENTAL STUDY OF THE GAS-PHASE HYDROFLUORINATION OF PERCHLOROETHYLENE OVER A CHROMIUM-BASED CATALYST
A.A. Zirka, S.I. Reshetnikov
React. Kinet. Catal. Lett., 88(2) (2006) pp. 399-404.
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.
KINETIC BEHAVIOR OF BENZENE HYDROGENATION AND THIOPHENE HYDROGENOLYSIS ON SULFIDE Ni-Mo/Al2O3 CATALYST
E.A. Ivanov, S.I. Reshetnikov, M.V. Sidyakin, A.N. Startsev
React. Kinet. Catal. Lett., 88(2) (2006) pp. 325-332.
An unsteady-state kinetic model of both benzene hydrogenation (HDA) and thiophene hydrogenolysis (HDS) on a 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.
MATHEMATICAL MODEL OF UNSTEADY STATE PROCESSES IN A MULTI-SECTIONAL SYMMETRIC CATALYTIC REACTOR
V.I. Drobyshevich*, L.V. Yausheva, N.A. Chumakova, E.V. Sazhenkova, A.S. Noskov
(*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia)
Siberian J. Ind. Appl. Math., VIII, 3(23) (2005) pp. 48-57.
Mathematical model of unsteady state processes in a multi-sectional symmetric catalytic reactor with periodic changes of the input gas flow direction is developed. The peculiarity of this apparatus is as follows: the fixed bed consists of six granular layers, in the outer layers of an inert material, there are no chemical reactions proceeding, while in two next layers the catalytic reactions take place, and in two central layers of an inert granular substance the homogeneous reactions proceed. Moreover, after the third part of the fixed bed a part of the gas flow is directed out from the reactor into an outer heat exchanger. In the case in hands, the coefficients of the two-phase one-dimensional model are step functions. The significant difference in the intensity of the homogeneous and catalytic reactions leads to some high gradients which propagate along the computational region in the dynamical operation. In the paper an efficient algorithm is suggested for numerical studies of the model. It is based on the balanced monotonic difference schemes. The dynamics of periodic solution formation is described and the periodic operation parameters are studied.
MODELING OF STEAM REFORMING OF NATURAL GAS USING CATALYSTS WITH GRAINS OF COMPLEX SHAPES
A.P. Kagyrmanova, I.A. Zolotarsky, N.V. Vernikovskaya, E.I. Smirnov, V.A. Kuzmin, N.A. Chumakova
Theor. Found. Chem. Eng., 40(2) (2006) pp. 155-167.
A mathematical model is developed to describe steam reforming of natural gas in a catalyst grain and a catalyst bed. The model differs from the published ones by a detailed description of the processes in a catalyst grain and the mechanisms of radial heat and mass transfer, including for catalyst grains of complex shape. The model parameters are numerically analyzed, and the efficiencies of catalyst grains of different shapes and sizes are compared.
REGENERATION OF A CATALYTIC FILTER IN THE PRESENCE OF HIGHLY FLAMMABLE HYDROCARBONS IN SOOT
T.L. Pavlova, N.V. Vernikovskaya, N.A. Chumakova, A.S. Noskov
Combust., Explosion, Shock Waves, 42(4) (2006) pp. 396-402.
The dynamical process of oxidative regeneration of a catalytic particulate filter made of a fibrous material is analyzed theoretically by mathematical modeling. The model describes the dynamics of temperature and concentrations of gaseous composition and soot particles in the filter wall. The effect of the controlled rate of the input temperature increase and the presence of highly flammable hydrocarbons in exhaust gases entering the filter is demonstrated.
AUTOMATION OF CALCULATIONS OF CHEMICAL-TECHNOLOGICAL SCHEMES OF CATALYTIC PROCESSES
I.V. Bukreeva, Yu.V. Malozemov, V.S. Kharitonov, A.S. Shmelyov, S.I. Reshetnikov, I.A. Zolotarsky
Catal. Ind., 4 (2006) pp. 24-29.
Application of information-computer complexes has been considered for implementation of computer calculations of complex chemical-technological schemes of catalytic processes. The most general principles of their formulation and architecture are given. Taken one of them (FLOCAS) as an example, its structure and the main directions of use are shown, for example, the development of new chemical- technological productions and optimization of current ones, analysis of technical proposals, searching the optimal operations of equipment operation, and others.
APPLICATION OF THE CHEMPAK PACKAGE FOR MODELING OF GAS-DYNAMICS REACTOR
V.A. Vshivkov*, G.G. Chernykh*, O.P. Sklyar, A.V. Snytnikov**
(*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia; **Novosibirsk State University, 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.
SIMULATION OF THE THREE-DIMENSIONAL DYNAMICS OF MATTER IN THE GRAVITATIONAL FIELD USING MULTIPROCESSOR COMPUTERS
V.A. Vshivkov*, V.N. Snytnikov, N.V. Snytnikov**
(*Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia; **Novosibirsk State University, Novosibirsk, Russia)
Comput. Technol., 11(1) (2006) pp. 15-27.
A numerical model for investigation of the 3D motion of matter in a gravitational field is proposed. The model satisfies all fundamental conservation laws. For acceleration of computations an effective parallel algorithm for use on multiprocessor computers with distributed memory is implemented. The results of the numerical experiments with the initial distribution of matter in the form of a plane disk are presented. These experiments are aimed to define the parameters' values, which lead to the stability of the disk with respect to asymmetrical disturbances directed along the axis of rotation and to the spiral gravity waves.
INVESTIGATION OF FINE GRANULAR MATERIAL FLOW THROUGH A PACKED BED
A.V. Matveev*, L.V. Barysheva, I.V. Koptyug*, V.M. Khanaev, A.S. Noskov
(*International Tomography Center, Novosibirsk, Russia)
Chem. Eng. Sci., 61(8) (2006) pp. 2394-2405.
Three different methods cut-off, time-of-flight, and Pulsed Field Gradient Nuclear Magnetic Resonance were used to study downstream flow of fine granular material through the fixed bed reactor. For describing the transport of solid particles within a fixed granular bed, a model has been developed. In time-of-flight and cut-off techniques the highest average velocity of filtration is observed at the lowest mass flow rate in all experimental traces, while upon the flow rate increase it tends to an asymptotic value. Experimental results obtained by pulsed field gradient nuclear magnetic resonance technique have revealed the bimodal character of particles velocities distribution. The average filtration velocity has a maximum at an intermediate mass flow rate close to the bed flooding, in contrast to the results obtained by cut-off and time-of-flight methods. The velocities measured using all three techniques were compared by converting them into dimensionless values. From the experimental results, the values of model parameters have been evaluated which allowed to describe particle velocities within a bed.
MATHEMATIC MODELING OF THE PROCESS OF PRODUCTION OF NANOFIBROUS CARBON FROM METHANE IN AN ISOTHERMAL REACTOR WITH A FIXED BED OF THE Ni–Al2O3 CATALYST
S.G. Zavarukhin, G.G. Kuvshinov*
(*Novosibirsk State Technical University, Novosibirsk, Russia)
Chem. Eng. J., 120(3) (2006) pp. 139-147.
The process of synthesis of nanofibrous carbon from methane achieved in an isothermal plug flow reactor with a fixed bed of catalyst 90 wt.% Ni–Al2O3 is considered. It is shown that the equations allow a solution in the form of a progressive wave of deactivation that moves at a constant rate and has a stationary profile. Analytic dependencies are obtained to calculate the wave rate and carbon content in the deactivated catalyst. The process parameters are calculated at 823 K and specific methane consumption 120 l/h g. The process parameters are compared for two types of reactors operating at identical conditions: a plug flow reactor with the fixed catalyst bed and a reactor with perfect mixing of catalyst particles and gas. The specific carbon yield is shown to be higher in the latter.
OXYGEN DIFFUSION IN NANOSTRUCTURED PEROVSKITES
I.L. Zhogin*, A.P. Nemudry*, P.V. Glyanenko*, Yu.M. Kamenetsky*, H.J.M. Bouwmeester**, Z.R. Ismagilov
(*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Institute for Nanotechnology, University of Twente, The Netherlands)
Catal. Today, 118(1-2) (2006) pp. 151-157.
Nonstoichiometric perovskite-related oxides (e.g. ferrites and cobaltites, etc.) are characterized by fast oxygen transport at ambient temperatures, which relates to the microstructural texturing of these materials, consisting wholly of nanoscale microdomains. A heterogeneous diffusion model to describe the kinetics of oxygen incorporation into nanostructured oxides have been developed. Nanodomain boundaries are assumed to be the high diffusivity paths for oxygen transport whereas diffusion into the ordered domains proceeds much slower. The model has been applied for qualitative evaluation of oxygen diffusion parameters from the data on wet electrochemical oxidation of nanostructured perovskite SrCo0.5Fe0.2Ta0.3O3−y samples. Using Laplace transform methods, an exact solution is found for a ramped step-wise potential, allowing fitting of the experimental data to theoretical curves (in Laplace transforms). A further model generalization is considered by introducing additional parameters for the size distribution of domains and particles.
DEVELOPMENT OF PORTABLE HYDROGEN GENERATOR USING CHEMICAL HYDRIDE
V.I. Simagina, P.A. Storozhenko*, O.V. Komova, O.V. Netskina
(*State Research Institute of Chemistry and Technology of Organoelement Compounds, Moscow, Russia)
Int. Sci. J. Alternative Energy Ecol., 7 (2006) pp. 29-30.
Application of portable fuel cells raises the problem of creation of hydrogen compact sources. At present several types of protable hydrogen generators for fuel cells are offered, including the perspective generators based on hydrolysis of hydrides – sodium borohydride and ammonia-borane. Joint efforts of State Research Institute of Chemistry and Technology of Organoelement Compounds and Boreskov Institute of Catalysis allow to develop portable systems for hydrogen generation on the basis of sodium borohydride hydrolysis with optimized mass and size properties. In this study was found that Ru and Rh catalysts supported on untraditional LiCoO2 carrier and TiO2 show the highest activity in NaBH4 hydrolysis in comparison with catalysts prepared using traditional supports - γ-Al2O3, TiO2, carbonaceous material. Carried out studies have permitted to develop the optimized design of portable hydrogen generator with automatic control system.
THERMOLYSIS OF α-PINENE IN SUPERCRITICAL LOWER ALCOHOLS
A.M. Chibiryaev*, V.I. Anikeev, A. Yermakova, P.E. Mikenin, I.V. Kozhevnikov**, O.I. Salnikova*
(*Vorozhtsov Novosibirsk Institute of Organic Chemistry, Novosibirsk, Russia; **University of Liverpool. Liverpool, UK)
Russ. Chem. Bull., 54(8) (2005) pp. 987-992.
Thermal isomerization of α-pinene in supercritical solvents, viz., ethanol, methanol, and propan-1-ol, was carried out, and differences in the rate and selectivity of the process were revealed. In supercritical ethanol the reaction rate increases sharply and the selectivity remains unchanged with an increase in the temperature (from 290 to 390°C) or pressure (from 90 to 270 atm). The main reaction products are limonene, isomeric alloocimenes, and pyronenes. The selectivity for limonene in propan-1-ol is higher than in other alcohols when the conversion of α-pinene is not higher than 50%. In supercritical ethanol (430°C, 120 atm, 140 s) limonene is more stable than α-pinene (conversion 8%).
RESULTS OF TESTING THE PLANT FOR SUPERCRITICAL WATER OXIDATION OF NITROGLYCERIN AND DIETHYLENE GLYCOL DINITRATE
V.I. Anikeev, N.S. Belobrov*, R.N. Piterkin*, R.Sh. Prosvirnin*, L.S. Zvolsky*, P.E. Mikenin, A. Yermakova
(*Federal Research and Production Center "Altai", Biysk, Russia)
Ind. Eng. Chem. Res., 45(24) (2006) pp. 7977-7981.
In Russia, the first stationary supercritical water oxidation (SCWO) pilot plant for the oxidation of industrial wastes at an operating factory with a tubular flow reactor and a capacity of about 40 kg/h wastewater has been created on the basis of fundamental investigations. It allowed for the elimination of a mixture of nitroglycerin and diethylene glycol dinitrate in the wastewater with very high efficiency. Acetone was used as the fuel, and hydrogen peroxide or air was used as the oxidant.
PURIFICATION OF DETONATION PRODUCTS FROM TOXIC COMPOUNDS
V.P. Isakov*, V.G. Isakova**, Z.P. Pai
(*Krasnoyarsk State University, Krasnoyarsk, Russia; **Kirenskii Institute of Physics, Krasnoyarsk, Russia)
In “Shock-Assisted Synthesis and Modification of Materials”, Eds. A.A. Deribas, Yu.B. Scheck, Moscow: Torus Press Ltd., 2006, 176 pp.
In this work, various systems for purification of gaseous detonation products from toxic constituents are tested. Ammonite and hexogen charges were exploded in a blasting camera. Hexogen contained the admixture of Cu and Al2O3 powders. Purification of gases from solid particles was performed with a centrifugal bubble apparatus containing a gas-liquid layer wetted with a cuprammonium solution. This technique turned out effective for entrapping carbon compounds and dust but insufficient for nitrogen- and sulfur-containing compounds. For this reason, also was tested the absorber based on phosphor ammonium salts developed at the Boreskov Institute of Catalysis. The content of hazardous gases was detected with a portable chromatograph AkhG-002-01.
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
In “Materials in Clean Power Systems: Applications, Corrosion, and Protection”, Eds. Z.G. Yang, K.S. Weil, M.P. Brady, TMS (The Minerals, Metals & Materials Society), 2006, pp. 25-38.
The research concerns the problems emerged from a short contact time adiabatic reactor operation in a pilot plant scale. Hydrogen-rich gas was generated by selective catalytic oxidation of gasoline over monolithic catalysts with the composite ceramometal and metallic supports. For the purpose of thermodynamic consideration of the process gasoline was simulated by a mixture of 28 organic compounds. It was demonstrated, that over the range of operational parameters required for syngas generation nearly equilibrium synthesis gas was produced. Some bottlenecks of the process performance are considered. Pre-reforming of fuel with releasing of some chemical energy before the catalyst can be observed in the monolith reactor. Breakthrough of the feed could arise near the reactor wall in a certain case. Feed composition, superficial velocity and design factors affect the phenomena mentioned.
THERMODYNAMIC ANALYSIS OF A SOLID OXIDE FUEL CELL POWER SYSTEM WITH EXTERNAL NATURAL GAS REFORMING
V.D. Meshcheryakov, V.A. Kirillov, V.A. Sobyanin
Theor. Found. Chem. Eng., 40(1) (2006) pp. 51-58.
A thermodynamic analysis of a solid oxide fuel cell power system is performed using conditions of thermodynamic equilibrium in a prereformer of natural gas to synthesis gas and a solid oxide fuel cell battery. It is shown that a thermally coupled steam reformer of natural gas provides a significantly higher efficiency of conversion of fuel energy to electric energy than other types of reformers.
PHENOL OXIDATION IN SUPERCRITICAL WATER IN A WELL-STIRRED CONTINUOUS REACTOR
A. Yermakova, P.E. Mikenin, V.I. Anikeev
Theor. Found. Chem. Eng., 40(2) (2006) pp. 168-174.
A well-stirred reactor for phenol and acetic acid oxidation in supercritical water is considered. A mathematical model of an adiabatic reactor is formulated. A numerical algorithm for solving the model equations using the homotopy method is developed. The model takes into account specific features of processes under supercritical conditions, namely, the changes in the thermodynamic properties (enthalpy, heat capacity, and critical parameters) of mixtures with a change in pressure and temperature. The thermodynamic properties are calculated by methods of nonideal thermodynamics. It is shown that there is a multiplicity of steady-state solutions at various reactor performances. The results of numerical analysis of the effect of the inlet flow temperature, the amount of methanol (fuel) fed, and the total pressure on the reactor performance are presented.
MASS TRANSFER IN A MEDIUM WITH A RAPIDLY RENEWED INTERFACE
A.O. Kuzmin, V.N. Parmon, M.Kh. Pravdina*, A.I. Yavorskii**, N.I. Yavorskii**
(*Kutateladze Institute of Thermophysics, Novosibirsk, Russia; **Novosibirsk State Technical University, Novosibirsk, Russia)
Theor. Found. Chem. Eng., 40(2) (2006) pp. 225-232.
Specific features of the mass transfer in a medium with a rapidly renewed interface are theoretically analyzed. It is shown that, in the case of intense renewal of the interface, if the adsorption of gas molecules on the liquid surface is taken into account, an additional number of molecules of the substance being dissolved are transferred to the bulk of the liquid by convective transfer of surface adsorption layers. If this process is taken into account, there is an additional mass flux into the liquid and, consequently, the mass-transfer rate is higher. In particular, this allows one to increase the concentration of the substance being dissolved above the thermodynamically equilibrium value in the absence of chemical reaction. Types of mass-transfer apparatuses in which the considered mode can be realized are discussed.
MULTICAPILLARY COLUMNS FOR CHROMATOGRAPHY
Y.P. Belov*, M.M. Ulyanova**, V.N. Sidelnikov
(*ChromBA, Inc., State College, USA; **State Public Health Labs, Anchorage, USA)
Am. Lab., 37(6) (2005) pp. 42-46.
The principles and theory of high-speed capillary chromatography have been known since the 1960s. To realize the maximum speed capabilities, it is necessary to use capillaries with a diameter of approx. 5–50 µm. However, capillary columns with a diameter smaller than 100 µm are rarely used because they require very small sample quantities that are difficult to inject and detect. To overcome this problem, multicapillary columns (MCCs) composed of a large number of capillaries were developed. Due to much larger surface and cross-sectional areas, MCCs overcome the flow rate, volume, and sample capacity limitations associated with single-capillary columns. MCCs are compatible with standard chromatographic equipment and work with all common sample sizes and injection techniques. No extensive modifications of the injector and detector are needed.
SOL-GEL MULTICAPILLARY COLUMNS FOR GAS-SOLID CHROMATOGRAPHY
V.N. Sidelnikov, Yu.V. Patrushev, Y.P. Belov*
(*ChromBA, Inc., State College, USA)
J. Chromatography A, 1101 (2006) pp. 315-318.
In this work, the method is reported for the preparation of multicapillary columns (MCCs) for gas-solid chromatography. The porous layer adsorbent is formed on capillary walls by the hydrolysis of aluminum alkoxide in the presence of polypropylene glycol (PPG) and HCl. Porosity and selectivity of the adsorbent depend on reaction conditions and the concentration of PPG. Sol-gel MCCs are well suited for high-speed chromatographic analysis of light hydrocarbons by gas-solid chromatography. Nine- component mixtures of C1-C4 hydrocarbons are separated within 8-12 s. The efficiency of 25-30 cm long alumina sol-gel MCCs consisting of approximately 1400 capillaries of 40 microm diameter is up to 2500-3000 theoretical plates.
SUPERFAST CHROMATOGRAPHY AND ITS POTENTIALITIES IN CATALYTIC STUDIES
V.N. Sidelnikov
In “Industrial Catalysis. Lectures”, Ed. A.S. Noskov, Moscow, Kalvis, 2006, pp. 7-29.
The paper deals with approaches to accelerating processes of chromatographic analysis. The application of short capillary columns with a small (10 to 50 μm) diameter of capillaries is shown to be most efficient for shortening the separation time. There are limitations in employing the columns, the principal one being the necessity of injection of a very small sample volume. This limitation can be circumvented using not one but a great bunch of small-diameter capillaries; the bunch behaves like a chromatographic column referred to as polycapillary column (PCC). In this case the sample injected to the column can be increased in volume to allow the operation over a wide concentration range. Under discussion are the PCC properties and the mechanism of broadening of the chromatographic peak. The PCC applications for gas- liquid and gas adsorption chromatography are exemplified. An example of catalytic application of PCC also is considered.
THE STATE AND PROSPECTS OF DEVELOPMENT OF CATALYST SUBINDUSTRY AND CATALYTIC DEVELOPMENTS IN RUSSIA
V.N. Parmon, A.S. Noskov, N.P. Anfimova, V.P. Shmachkova
Catal. Ind., 1 (2006) pp. 6-20.
An analysis of the current state of the catalytic
production in Russia has been carried out compared with the world one. The attention is paid to the cardinal reorganization in the national economy that has resulted in the catastrophic cutting down of application of domestic catalysts in the key branches of the industry, thereby endangering the economical and, in some instances, political safety of our country. The main reasons of reducing the portion of the domestic catalysts in the processes of chemical, oil- refining, and petrochemical productions are generalized. The proposals are formulated that are related to the restructuring of the RF catalytic subindustry. The priorities in creation of new generations of catalysts and the development of the catalytic technologies for a period of 2006–2015 are considered. It is shown that the innovative factors in the catalyst producing subindustry, being the most science-intensive one among the other branches of the chemical complex, are determinant mainly for the resource saving and energy efficiency of the base large-scale productions. The changeover to the new generations of catalysts appreciably improves the depth of fresh raw material processing and decreases the quantity of waste being formed.
FIBERGLASS CATALYSTS FOR DIESEL EXHAUST-GAS PURIFICATION
D.A. Arendarskii, A.N. Zagoruiko, B.S. Bal’zhinimaev
Chem. Sustain Devel., 13(6) (2005) pp. 731-735.
Results of laboratory and pilot tests of fiberglass catalysts for diesel exhaust-gas purification are presented. It is shown that such catalysts provide high oxidation level of CO and hydrocarbons, and also reduction of nitrogen oxides in exhaust gases of real diesel engines.
NITROGEN OXIDES REMOVAL FROM EXHAUSTS GASES OF DIESEL ENGINES: PROBLEMS AND PROSPECTS
V.A. Sadykov, T.G. Kuznetsova, R.V. Bunina, G.M. Alikina, L.Ch. Batuev, V.A. Sobyanin, V.A. Kirillov, V.P. Doronin*, V.A. Matyshak**, A.Ya. Rozovskii***, V.F. Tretyakov***, T.N. Burdeinaya***, V.V. Lunin****, J. Ross*****
(*Institute of Hydrocarbons Processing, Omsk, Russia; **Semenov Institute of Chemical Physics, Moscow, Russia; ***Topchiev Institute of Petrochemical Synthesis, Moscow, Russia; Moscow Lomonosov State University, Moscow, Russia; *****University of Limerick, Limerick, Ireland)
Chem. Sustain. Devel., 13(6) (2005) pp. 713-724.
The paper presents estimation of opportunities of application of new technologies for nitrogen oxides removal from diesel exhaust gases based on stationary and non-stationary processes of nitrogen oxides reduction by diesel fuel or products of its selective conversion to syn-gas or olefins in package generators. Using syn-gas in the mixture with main fuel for gasoline engine or diesel allows sharply reduce the emissions of harmful substances and increase the efficiency of engines, especially upon using of ultra-poor mixtures. Availability of using complex oxide systems with high oxygen mobility as catalysts for the processes of soot particles oxidation with nitrogen oxides, promoting removal of both types of harmful impurities, is shown.
CATALYSTS ON THE BASE OF COMPLEX OXIDES WITH PEROVSKITE- AND FLUORITE-LIKE STRUCTURES FOR SOOT REMOVAL FROM DIESEL EXHAUSTS
T.G. Kuznetsova, V.A. Sadykov, V.A. Matyshak*, L.Ch. Batuev, V.A. Rogov
(*Semenov Institute of Chemical Physics, Moscow, Russia)
Chem. Sustain Devel., 13(6) (2005) pp. 779-785.
Reaction of soot oxidation in mixture О2 + He and O2 + NO2 + He is studied over substituted perovskites based on lanthanum manganites, and modified fluorites based on solid solution Ce-Zr-O, including those doped with Pt. It is shown, that efficiency of soot oxidation is higher for the mixture, containing NO2. It is established, that necessary condition for initiation of soot oxidation is the presence of weakly bonded surface oxygen, and for the process of developed soot oxidation – mobility of lattice oxygen.
FORMATION AND DECOMPOSITION OF ETHANE, PROPANE, AND CARBON DIOXIDE HYDRATES IN SILICA GEL MESOPORES UNDER HIGH PRESSURE
E.Y. Aladko*, Y.A. Dyadin*, V.B. Fenelonov, E.G. Larionov*, A.Y. Manakov*, M.S. Melgunov, F.V. Zhurko*
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Phys. Chem. B, 110(39) (2006) pp. 19717-19725.
The experimental data on decomposition temperatures for the gas hydrates of ethane, propane, and carbon dioxide dispersed in silica gel mesopores are reported. The studies were performed at pressures up to 1 GPa. It is shown that the experimental dependence of hydrate decomposition temperature on the size of pores that limit the size of hydrate particles can be described on the basis of the Gibbs-Thomson equation only if one takes into account changes in the shape coefficient that is present in the equation; in turn, the value of this coefficient depends on a method of mesopore size determination. A mechanism of hydrate formation in mesoporous medium is proposed. Experimental data providing evidence of the possibility of the formation of hydrate compounds in hydrophobic matrixes under high pressure are reported. Decomposition temperature of those hydrate compounds is higher than that for the bulk hydrates of the corresponding gases.
EQUILIBRIUM CONDITIONS FOR DECOMPOSITION OF GAS HYDRATES, DISPERSED IN MESOPOROUS MEDIUM
E.Ya. Aladko*, Dyadin*, F.V. Zhurko*, E.G. Larionov*, M.S. Melgunov, A.Yu. Manakov**, A.N. Nesterov**, V.B. Fenelonov
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Gas Indust., Special Edition: Gas Hydrates (2006) pp. 18-27.
Considerable part of natural gas hydrates localized in permafrost or in near-bottom sea and ocean areas are the inclusions in the space between average and fine fractions of sediments. Equilibrium thermodynamic conditions of such hydrate decomposition may depend on the size of enclosing rocks. The influence of medium pore size on the decomposition temperatures for the dispersed gas hydrates is discussed quantitatively in the work.
HYDROGEN PURIFICATION FOR FUEL CELLS BY CARBON MONOXIDE SELECTIVE METHANATION
T.P. Minyukova, I.Sh. Itenberg, M.P. Demeshkina, N.V. Shtertser, T.M. Yurieva
Chem. Sustain. Devel., 13(6) (2005) pp. 793-796.
Possibility of fine hydrogen cleaning from CO by method of preferential hydrogenation of carbon oxide (II) to methane up to residual CO content 1000 ppm is studying. Efficient nickel-containing catalyst is suggested for creation of package unit for hydrogen treatment for fuel cells providing desired cleaning result (≤ 1000 ppm CO at the outlet), selectivity (≥ 70 % of methane forms from CO) and activity (contact time ≤ 6000 h-1).
STUDIES OF THE REACTION BETWEEN CF2Cl2 AND NANOCRYSTALLINE MgO USING A TEOM MICROANALYZER
I.V. Mishakov, A.A. Vedyagin, A.F. Bedilo, M.S. Melgunov, R.A. Buyanov
Doklady Phys. Chem., 410(1) (2006) pp. 251-254.
Potentialities of the new approach to mass measuring provided in a TEOM microanalyzer are demonstrated with the topochemical reaction of Freon CF2Cl2 with nanodispersed MgO conducted in the flow mode. The induction period of 5 min (375°C) to two hours (300°C) is established to occur; after that the reaction is the fast phase of magnesia to fluoride transformation. The nature of the induction period and the mechanism of the topochemical reaction until its accomplishment are elucidated. Unordinary profiles of temperature and reaction rate of MgO to MgF2 transformation are discovered and interpreted; these are accounted for by variations in the molar volume of the solid phase and by its cracking during the chemical phase transformations. Application of the TEOM microanalyzer makes it possible to determine the activation energy of the reaction. As the first approximation, the mechanism is a combination of topochemical stages involving cleavage of chemical bonds and exchange between oxygen and fluorine atoms. The obtained activation energy is an apparent quantity; it characterizes a total of energetic set of stages.
POTENTIALITIES OF GRAVIMETRY FOR ECOLOGICAL AIR MONITORING
A.A. Vedyagin, I.V. Mishakov, A.I. Nizovskii
Omsk Sci. Bull., 2(35) (2006) pp. 144-147.
Authors considered the contemporary ways to monitor an atmospheric contaminations by gravimetric method based on TEOM analyzer. An examples of using the said method to determine continuously aerosol and PM concentration in air as well as micro-impurities and vapors of organic compounds are discussed.