A catalyst is a substance that accelerates a chemical reaction without itself being changed. They are essential in refining petroleum products and manufacturing pharmaceuticals, plastics, food additives, fertilizers, green fuels, industrial chemicals, and more.
Scientists and engineers have been fine-tuning catalytic reactions for decades, but it is currently impossible to directly observe these reactions at the extreme temperatures and pressures often associated with industrial-scale catalysis. I don’t know exactly what’s going on with nano because it’s possible. atomic scale.
Now, in a groundbreaking computational chemistry study, chemical engineers at the University of Wisconsin-Madison have developed a new model of how these catalytic reactions work.
This understanding will enable engineers and chemists to develop more efficient catalysts and tune industrial processes. Considering that 90% of the products we encounter in our lives are manufactured at least in part by catalysis, the potential for significant energy savings is significant. In fact, just three catalytic reactions—steam methane reforming to produce hydrogen, ammonia synthesis to produce fertilizer, and methanol synthesis—use nearly 10% of the world’s energy.
“Reducing the temperature at which these reactions must be carried out by just a few degrees would greatly reduce the energy demands facing humanity today,” says Manos Mabrikakis, a professor of chemistry and bioengineering. UW-Madison, who led the research. “Reducing the energy required to run all these processes also reduces our environmental footprint.”
Mavrakis, postdocs Lang Xu, Konstantinos G. Papanikolaou, and graduate student Lisa Je published the news of their progress in the April 7, 2023 issue of Science.
In their research, UW-Madison engineers developed and used powerful modeling techniques to simulate catalytic reactions at the atomic scale. In this study, reactions involving transition metal catalysts in the form of nanoparticles, including platinum, palladium, rhodium, copper, nickel, and other elements important in industry and green energy, were investigated.
According to the current rigid surface model of catalysis, the tightly packed atoms of transition metal catalysts provide a 2D surface on which chemical reactants attach and participate in reactions. When sufficient pressure and heat or electricity are applied, the bonds between atoms within the chemical reactants are broken, allowing the fragments to recombine into new chemical products.
“The general assumption is that these metal atoms are tightly bound to each other and merely provide ‘landing spots’ for reactants. Everyone assumes that the intermetallic bonds remain intact during the reaction that catalyzes them,” he says Mavrakis. “So, for the first time, we asked the question, ‘Will the energy to break the bonds of the reactants be as much as the energy required to break the bonds in the catalyst?'”
According to Mavrakis modeling, the answer is yes. The energy provided for many catalytic processes to take place is sufficient to break bonds and free single metal atoms (known as adatoms) to begin moving across the surface of the catalyst. These adatoms bind into clusters and serve as sites on the catalyst, allowing chemical reactions to occur much more easily than on the original hard surface of the catalyst.
Using a series of special calculations, the team explored the industrially important interactions of eight transition metal catalysts and 18 reactants to determine the potential energy levels and temperatures to form such small metal clusters. , and the number of atoms in each cluster. It greatly affects the reaction rate.
Their experimental collaborators at the University of California, Berkeley, used atom-resolved scanning tunneling microscopy to observe the adsorption of carbon monoxide on nickel (111). Their experiments suggest that models showing various imperfections in the structure of the catalyst can also affect how single metal atoms are released and how reactive sites are formed. I have confirmed that there is.
Mavrakis says the new framework challenges the fundamentals of how researchers understand catalysis and how it happens. This may also apply to other non-metallic catalysts and will be investigated in future work. It is also relevant to understanding other important phenomena related to corrosion and tribology, or surface interactions during motion. “We are revisiting some very established assumptions in understanding how catalysts work and more generally how molecules interact with solids. he says.
Original: New atomic-scale understanding of catalysis could unlock significant energy savings
Than: University of Wisconsin-Madison | University of California, Berkeley
