Upending a long-held supposition, MIT researchers discovered that a common catalyst works by cycling between two different forms. The finding could lead to improved catalysts for industrial reactions.
The process of catalysis — in which a material speeds up a chemical reaction — is crucial to the production of many of the chemicals used in our everyday lives. But even though these catalytic processes are widespread, researchers often lack a clear understanding of exactly how they work. A new analysis by researchers at MIT has shown that an important industrial synthesis process, the production of vinyl acetate, requires a catalyst to take two different forms, which cycle back and forth from one to the other as the chemical process unfolds. Previously, it had been thought that only one of the two forms was needed. The new findings are published today in the journal Science, in a paper by MIT graduate students Deiaa Harraz and Kunal Lodaya, Bryan Tang PhD '23, and MIT professor of chemistry and chemical engineering Yogesh Surendranath. There are two broad classes of catalysts: homogeneous catalysts, which consist of dissolved molecules, and heterogeneous catalysts, which are solid materials whose surface provides the site for the chemical reaction. "For the longest time," Surendranath says, "there's been a general view that you either have catalysis happening on these surfaces, or you have them happening on these soluble molecules." But the new research shows that in the case of vinyl acetate — an important material that goes into many polymer products such as the rubber in the soles of your shoes — there is an interplay between both classes of catalysis. "What we discovered," Surendranath explains, "is that you actually have these solid metal materials converting into molecules, and then converting back into materials, in a cyclic dance." He adds: "This work calls into question this paradigm where there's either one flavor of catalysis or another. Really, there could be an interplay between both of them in certain cases, and that could be really advantageous for having a process that's selective and efficient." The synthesis of vinyl acetate has been a…