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A simple technique that uses a small amount of energy can increase the efficiency of some important chemical processing reactions by a factor of 100,000, MIT researchers report. These reactions are at the heart of petrochemical processing, pharmaceutical manufacturing, and many other industrial chemical processes.

The surprising findings are reported today in the journal scienceIn a paper by MIT graduate student Karl Westendorff, professors Yogesh Surendranath and Yuri Roman Leshkov, and two others.

“The results are really surprising,” says Surendra Nath, professor of chemistry and chemical engineering. Rate increases of this magnitude have been observed before, but in a different class of catalytic reactions called redox half-reactions, in which electrons are gained or lost. The dramatically increased rates in the new study “have never been observed for reactions that do not involve oxidation or reduction,” he says.

The non-redox chemical reactions studied by the MIT team are catalyzed by acids. “If you’re a first-year chemistry student, the first type of catalyst you’ll probably learn about is an acid catalyst,” says Surendranath. There are hundreds of such acid-catalyzed reactions, “and they are critical in everything from processing petrochemical feedstocks to making commodity chemicals to transforming pharmaceutical products. The list goes on.”

“These reactions are key to making many of the products we use every day,” says Roman Leshkov, professor of chemical engineering and chemistry.

But those who study redox half-reactions, also known as electrochemical reactions, are part of an entirely different research community than those who study non-redox chemical reactions, known as thermochemical reactions. . As a result, although the technique used in the new research, which involved applying a small external voltage, was well known in the electrochemical research community, it was not known for the acid-induced thermochemical reactions. but was not systematically implemented.

People working on thermochemical catalysis, says Surendra Nath, “generally don’t consider the role of the electrochemical potential at the catalyst surface,” and often don’t have good ways to measure it. And this study What this tells us is that relatively small changes, on the order of a few hundred millivolts, can have huge effects — orders of magnitude changes in the rate of catalytic reactions at these levels.”

“This neglected parameter of surface potential is something that we should pay a lot of attention to because it can have a really, really large effect,” he says. “It changes the paradigm of how we think about catalysis.”

Chemists traditionally think of surface catalysis as based on the chemical binding energy of molecules at active sites on a surface, which affects the amount of energy required for a reaction, he says. But the new findings show that the electrostatic environment is “just as important in defining the reaction rate.”

The team has already filed a provisional patent application on parts of the process and is working on ways to apply the findings to specific chemical processes. Westendorff says their findings show that “we need to design and develop different types of reactors to take advantage of such a strategy. And we are now working on scaling up these systems.” “

While their experiments so far have been conducted with two-dimensional planar electrodes, most industrial reactions are conducted in three-dimensional vessels filled with powder. Catalysts are distributed through these powders, which provide a large surface area for reaction. “We’re looking at how catalysis is currently done in industry and how we can design systems that take advantage of the infrastructure that’s already in place,” says Westendorf.

Surendra Nath adds that these new findings “raise the possibility of power generation: Is this a more general phenomenon? Does electrochemical potential play a key role in other classes of reactions as well? In our mind, this Reshapes how we think about designing catalysts and promoting their reactions.”

Roman Leshkov adds, “Traditionally, people working in thermochemical catalysis do not associate these reactions with electrochemical processes at all. However, introducing this perspective to the community redefines it. will be how we can integrate electrochemical properties into thermochemical catalysis. This will have a big impact on the community in general.”

Although there has generally been little interaction between electrochemical and thermochemical catalysis researchers, Surendra Nath says, “This study shows the community that the line between the two has really been blurred, and that these two communities There is a great opportunity for cross-fertilization between

To make it work, “you have to design a system that’s unconventional for any given community to isolate that effect,” Westerdorf added. And that helps explain why such a dramatic effect has never been seen before. He notes that the editor of his paper also asked him why this effect had not been reported earlier. The answer lies in “how different those two ideas were before,” he says. “It’s not just that people don’t really talk to each other. There are deep differences in the way the two communities experience things. And this work is really, we think, a huge step toward bridging the two.” “

In practice, the results could lead to more efficient production of a variety of chemical materials, the team says. “You get orders of magnitude change in rate with very little energy input,” says Surendra Nath. “That’s the beauty of it.”

The results, he says, “build a more comprehensive picture of how catalytic reactions work at interfaces, regardless of whether you’re going to categorize them as electrochemical reactions or thermochemical reactions. ” “It’s rare that you find something that can revise our fundamental understanding of surface-catalyzed reactions in general. We’re very excited,” he added.

The team included MIT postdoc Max Hulsey Ph.D. ’22 and graduate student Theges Wesley Ph.D. ’23, and was supported by the Air Force Office of Scientific Research and the U.S. Department of Energy’s Basic Energy Sciences. was obtained.

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