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Версия для печати | Главная > Центр > Научные советы > Научный совет по катализу > ... > 2023 год > № 106

№ 106

 

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  • Валентин Николаевич ПАРМОН – к 75-летнему юбилею
  • 65 лет Институту катализа им. Г.К. Борескова СО РАН
  • VII Всероссийская научная молодежная школа-конференция «Химия под знаком Сигма исследования, инновации, технологии»
  • За рубежом
  • Приглашения на конференции
  • Памяти Зинфера Ришатовича ИСМАГИЛОВА



Валентин Николаевич ПАРМОН – к 75-летнему юбилею

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65 лет Институту катализа им. Г.К. Борескова СО РАН

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VII Всероссийская научная молодежная школа-конференция «Химия под знаком Сигма: исследования, инновации, технологии»

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An up-close view of catalysis in real time

Scientists observe how different temperatures alter interactions between metal nanoparticles and support material

One way to fight global warming is to capture carbon dioxide before it enters the atmosphere and convert it into something useful, such as methane, which can be a fuel or a chemical feedstock. That conversion, which bonds hydrogen atoms to carbon atoms, requires a catalyst, and now a group of researchers has uncovered how a certain class of catalysts can be treated to make them more efficient (Science 2023, DOI: 10.1126/science.adf6984).

Scientists have long known that placing a metal catalyst atop a different material could improve catalytic performance, a phenomenon called strong metal–support interaction (SMSI). The new study marks the first time researchers have actually seen in real time what’s going on in SMSI and how it can be adjusted for optimum performance.

The team set nickel nanoparticles atop titanium dioxide and used a combination of electron microscopy and vibrational spectroscopy to examine how individual atoms behaved when the catalyst was preheated and then exposed to CO2 and hydrogen. When they heated the catalyst to 400 °C, the TiO2 formed thin overlayers coating the nanoparticles. When they subsequently introduced the gases, the overlayers crawled off the nickel, leaving it completely exposed. With pretreatment to 600 °C, however, the titanium only slid off certain facets of the nanoparticle during catalysis, leaving the nickel only partially exposed. That left behind more interface sites between the titanium and the nickel where carbon reactions could take place, which made the catalysis more active and selective, working at a faster rate and creating fewer unwanted byproducts.

Bert Weckhuysen, a chemistry professor at Utrecht University in the Netherlands and one of the leaders of the work, says other temperatures probably lead to different amounts of interfaces between the materials, and he plans to study those to see if they give even better results. He also hopes to look at other SMSI systems, such as cobalt on titania.

Redesigning the nanoparticles to create different facets to which the overlayers cling might also provide a way to fine-tune the catalysis, says Sara Bals, a professor of physics at the University of Antwerp in Belgium and another leader of the study. “This is a completely new playground, and we look forward to exploring that new playground,” she says.

Wenyu Huang, a professor of chemistry at Iowa State University, calls the study “a substantial advancement” in the field. “This work will profoundly impact catalyst design for many important reactions that require harsh reaction conditions,” he says.

And Ding Ma, a professor of chemistry at Peking University in China not involved in the study, says the results are a “groundbreaking finding” in SMSI, which “has been the hot topic in catalysis.” He says the knowledge provided by the research “could be surely used to design new efficient/effective catalyst systems.”

 

Chemists make alkyl chlorides with less waste

Method swaps out oxidants and reductants for a visible-light catalyst

Chemists have figured out how to produce an industrially important reaction in a very economical way. Usually, adding a hydrochloric acid across a double bond involves two steps­—an oxidation and a reduction—and requires a 1:1 ratio of both the oxidant and the reductant. Now Tobias Ritter and coworkers at the Max Planck Institute for Kohlenforschung and RWTH Aachen University devised a method that requires only adding a photocatalyst and visible light to the starting material and hydrochloric acid (Nat. Catal. 2023, DOI:10.1038/s41929-023-00914-7). This new finding represents reactivity that’s the opposite of a well-established mechanism in organic chemistry, and it’s a way to make commodity chemicals with less waste. In college organic chemistry class, students usually learn about the Markovnikov rule: when adding a mineral acid across a carbon-carbon double bond, the compound that comes from the stablest carbocation is the one that will form. Anti-Markovnikov reactions, which have the opposite selectivity, are well known to come out of radical reactions of mineral acids, but these require some sort of stoichiometric initiator. This reaction does not, Ritter says. The researchers used cheap available mineral acids, such as HCl, and added them across simple olefins to form an alkyl chloride, he says. This is not the first time that chemists have made an alkyl chloride from an olefin, Ritter says. “There are a lot of other robust, cheaper methods than what we have here,” he says. But this is the first time anyone has done this reaction with high atom economy, he says. The real target for industrial chemists is taking a cheap feedstock chemical and adding water across a double bond to make primary alcohols, a starting material for a massive amount of industrial chemicals, Ritter says. This new method represents a step toward making those reactions with less waste.

 

Iron-rich meteorites and volcanic ash catalyzed prebiotic molecules on early Earth

Hydrogenation catalysts may have rained down on the early Earth

Researchers have long debated how the molecular components needed for life came to exist in the bleak environment of the early Earth about 4 billion years ago. Researchers now present experimental evidence for a new possibility–that metals from iron-rich meteorites pelting the planet from above, as well as from volcanic particles spewing from within, catalyzed the fixation of carbon dioxide, the dominant gas in the atmosphere at the time. This helped build basic carbon-​containing molecules such as hydrocarbons, aldehydes, and alcohols, which could then perform the reactions that generated more complex biotic molecules.

“We have closed a gap in the story of initiating life,” says Oliver Trapp, a chemist at Ludwig Maximilian University of Munich, who led the work (Sci. Rep. 2023, DOI: 10.1038/s41598-023-33741-8).

The idea hit Trapp like a meteorite—​literally. One day about 6 years ago, he was examining a meteorite he had purchased that was part of the Campo del Cielo, a cluster of meteorites thought to have fallen to Earth more than 4,000 years ago in Argentina. Reading the certificate listing the rock’s components–92% iron, 7% nickel, 0,5% cobalt, and a sprinkle of iridium—he imagined a meteorite hurtling through the atmosphere. It would slow down and heat up, causing the outside of the rocks to form nanoparticles. “Of course, these nanoparticles are highly reactive,” Trapp says. “I immediately realized this was the perfect Fischer-Tropsch catalyst.”

To test their idea experimentally, he and his colleagues made nanoparticles from meteorites and from volcanic ash and minerals. They put these materials into chambers that simulated a variety of atmospheric and climate conditions of that time–specifically, different atmospheric pressures and temperatures, different ratios of CO2 and hydrogen, and wet versus dry climate conditions. Across climate scenarios, the iron and other metals in the meteorite and ash particles catalyzed the synthesis of prebiotic molecules.

“Under [all] these conditions you are getting really, really similar compositions of these oxygenated compounds, which are really nice building blocks that can continue to generate chemistry,” Trapp says. Based on the rate of reactions observed, as well as estimates from other studies of ancient meteorite activity, the researchers calculated that this mechanism could have churned out 600,000 metric tons of these molecules per year, for tens to hundreds of millions of years. The team is now conducting large-scale simulation models and experiments to explore what kinds of reactions this initial prebiotic mixture molecules might have undergone and what larger compounds it might have produced.

“It’s surprising that chemists haven’t until recently systematically looked at how inorganic volcanic and meteoritic particles react with CO2,”, says Joseph Moran, a chemist at the University of Strasbourg. “The early Earth was producing hydrogen and hydrogenation catalysts were literally raining down from the sky,” Moran says. “Perhaps it is no coincidence that very ancient organisms were running their metabolisms on hydrogenation.”

Chemical & Engineering News



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