Baron Peters: Catalysis, Nucleation, and Reaction Rate Theory

For the past 11 years, Dr. Baron Peters has worked at the University of California, Santa Barbara as a Professor of Chemical Engineering and Chemistry. His work there was recognized by a National Science Foundation CAREER award in 2010 and a Camille Dreyfus Teacher-Scholar Award in 2013. Alumni from his group have become assistant professors at the University of Michigan and the Indian Institute of Technology Kanpur, staff engineers at three national laboratories, and research and development engineers in industry.

Peters studies the kinetics and mechanisms of chemical reactions using computational methods and theoretical analysis.

“In our work we are particularly interested in reaction rates, mechanistic hypothesis tests, and using natural time and length scale separations to construct multiscale models. These seem like niche topics, but they have several applications: catalysis, polymerization kinetics, nucleation and growth, and reactions in complex environments,” Peters said.

“We use a very broad tool set, which includes electronic structure calculations, molecular dynamics simulations, Monte Carlo, and population balance models. The common thread running through all of our work is the theory of rare events, fleeting transitions separated by long random waiting times.”

Missouri roots

Peters grew up in Moberly, a small town in Missouri. Although his current work involves a lot of math and computation, those interests didn’t blossom until he was older. As a child, he was interested in art, fishing, and sports and his first exposure to computers didn’t occur until his senior year of high school. He credits high school teachers for sparking an interest in math and science and inspiring him to apply to college. Peters started at the University of Missouri on a full scholarship in 1994.

Peters went on to major in chemical engineering and math. He continued his studies and earned a PhD in Chemical Engineering at UC-Berkeley, studying with Professors Arup Chakraborty and Alex Bell.

“I chose Berkeley because I had read some of Chakraborty’s fascinating papers as an undergraduate, and I was tempted by the mountains and trout streams of California,” Peters said. “In the Pitzer Center, I was surrounded by brilliant scientists who worked in reaction dynamics, quantum chemistry, and statistical mechanics. It was an enriching environment where students were constantly exposed to research outside of what their advisers did. My own PhD work ultimately did not like look like what my advisers focused on.”

As a postdoc with Professor Bernhardt Trout at MIT, Peters studied protein degradation mechanisms, activated gas diffusion in methane hydrates, solid-solid nucleation, and he developed path sampling-based mechanistic hypothesis testing tools that remain state-of-the-art.

Peters left Santa Barbara to join the Department of Chemical and Biomolecular Engineering at the University of Illinois in January 2019. To Peters’ great relief, all the members of his research lab decided to move with him to Illinois.

“At Santa Barbara, I had two great collaborations with Susannah Scott (in catalysis) and Mike Doherty (in crystallization). Modern funding models favor large teams with shared goals, and the smaller campus at Santa Barbara provided few opportunities to expand beyond those two collaborations,” explained Peters. “I chose the University of Illinois because they made me a great offer and because it has many excellent programs that overlap with my interests. I have met many faculty members within the Departments of Chemical and Biomolecular Engineering and Chemistry whose interests overlap with mine.”

Future directions
The Peters Lab has developed state-of-the-art models and simulation methods for nucleation in systems with multiple components. Their work on crystal nucleation and growth, which is funded by Eli Lilly, is focused on developing drugs with the correct crystal structures. The lab also has National Science Foundation and Department of Energy-funded projects on ethylene polymerization and amorphous catalysts.

“The Phillips ethylene polymerization catalyst makes about half the world’s polyethylene. However, it is still unclear how it works,” explained Peters. “It is an amorphous catalyst, so all of the sites are a little bit different, which makes it difficult to investigate them experimentally and theoretically.”

Several other catalysts also are made from amorphous materials. By building reliable computational tools for this family of catalysts, Peters hopes to understand how they work so that their properties can be systematically improved.

Teaching interests
Peters is teaching a new graduate course on kinetics and reaction engineering.

“For decades, this course has been taught with a focus on catalysis, but I’m working to make it a graduate-level kinetics course for every branch of chemical engineering. Everyone in the chemical sciences encounters kinetics, whether you’re growing crystals, making polymers, synthesizing nanoparticles, growing cells, or doing catalysis. Understanding the rate processes involved, formulating models that can predict changes in time and position is important. There are a lot of opportunities, applications, and challenges in those areas,”
he said.

While working in the disparate areas of catalysis, nucleation, and reaction rate theory, Peters noted some oddly persistent gaps between the chemistry, physics, and engineering perspectives on kinetics.

“Chemistry, chemical engineering, and chemical physics books cover almost mutually exclusive branches of kinetics, and advances from the last 40 years are all confined to the original literature, making them incomprehensible to most of the new PhD students. The key to progress in many areas is recognizing which theories are appropriate for which process, which tools can do the required calculations, and knowing how to stitch theories at different scales together into internally consistent models,” he explained.

To address these gaps in the literature, Peters published the first comprehensive kinetics textbook, Reaction Rate Theory and Rare Events, in 2017. The book is being used in graduate kinetics and reaction engineering courses in several chemical engineering departments.

In his spare time, Peters dabbles in pottery and likes backpacking and hiking. “I have taken my wife and kids, and sometimes my PhD students, on backpacking trips. Now that the kids and I are both getting older, I’m excited to let them carry my stuff for a change,” he said.

Written by Ananya Sen.