Published research in Science shows MIT scientists that the catalyst for vinyl acetate synthesis operates through periodic changes between two different molecular structures. The discovery proves that chemical transformations require multiple forms of catalysts to function efficiently. The research was conducted by Deiaa Harraz and Kunal Lodaya, Bryan Tang, Ph.D., and MIT professor of chemistry and chemical engineering Yogesh Surendranath and can be found here:
Harraz, D. M., Lodaya, K. M., Tang, B. Y., & Surendranath, Y. (2025). Homogeneous-heterogeneous bifunctionality in Pd-catalyzed vinyl acetate synthesis. Science, 388(6742). https://doi.org/10.1126/science.ads7913
The scientific field has divided catalysts into two general types: the dissolved molecules that operate within reaction media fall under homogeneous catalysts and heterogeneous catalysts provide reaction sites on solid surfaces. The MIT study demonstrates that vinyl acetate synthesis requires elements of both homogeneous catalysts and heterogeneous catalysts. The palladium reduces to the metallic Pd(0) state simultaneously with forming the soluble Pd(II) ionic state throughout the process. The heterogeneous catalyst acts as the key element to oxygen activation through its solid surface yet the homogeneous catalyst interacts with ethylene and acetic acid molecules. Yogesh Surendranath explained:
“For the longest time, there’s been a general view that you either have catalysis happening on these surfaces, or you have them happening on these soluble molecules.”
He went onto say:
“What we discovered, is that you actually have these solid metal materials converting into molecules, and then converting back into materials, in a cyclic dance.”
The study indicates that these two catalytic mechanisms establish an equilibrium which results in an efficient reaction process. Scientific research has made connections between these repetitive processes with corrosion mechanisms. Electrochemical forces drive state changes in the catalyst similar to the steps observed during rust formation. By borrowing methods from corrosion research; such as precise potential measurements, the team was able to identify the rate-limiting step in the catalyst’s conversion cycle.
For decades, the production of vinyl acetate has been refined using trial-and-error methods without a detailed mechanistic picture. The new design model allows engineers to combine advantages from homogeneous and heterogeneous systems as they create new catalyst designs. Research findings show that mixing surface reactions and molecular reactions might generate processes which achieve high selectivity with maximum efficiency.
The team borrowed techniques traditionally used in corrosion research to study the process. They used electrochemical tools to study the reaction, even though the overall reaction does not require a supply of electricity. By making potential measurements, the researchers determined that the corrosion of the palladium catalyst material to soluble palladium ions is driven by an electrochemical reaction with the oxygen, converting it to water. Lodaya stated:
“Corrosion is one of the oldest topics in electrochemistry, but applying the science of corrosion to understand catalysis is much newer, and was essential to our findings.”
The interplay between the two types of catalysis works efficiently and selectively. Surendranath says:
“because it actually uses the synergy of a material surface doing what it’s good at and a molecule doing what it’s good at,”
Harraz says.
“Now, with an improved understanding of what makes this catalyst so effective, you can try to design specific materials or specific interfaces that promote the desired chemistry,”
While the immediate impact on vinyl acetate production may be incremental, the broader significance of these findings lies in the potential for improved catalyst design across various industrial processes. Researchers and engineers are now encouraged to look at catalytic systems with fresh eyes, considering the potential benefits of cyclic transformations that were previously overlooked.
Hassan graduated with a Master’s degree in Chemical Engineering from the University of Chester (UK). He currently works as a design engineering consultant for one of the largest engineering firms in the world along with being an associate member of the Institute of Chemical Engineers (IChemE).
