Researchers at Washington State University have discovered self-sustaining oscillations in the Fischer-Tropsch process, an important industrial method for converting coal, natural gas, or biomass into liquid fuels. This breakthrough reveals oscillatory rather than steady-state behavior in reactions, which could lead to more efficient and controlled fuel production. This discovery provides a new knowledge-based approach to catalyst design and process optimization in the chemical industry.
Researchers at Washington State University have made significant progress in understanding the Fischer-Tropsch process, an important industrial method for converting coal, natural gas, or biomass into liquid fuels. They discovered that, unlike many catalytic reactions that maintain a steady state, the Fischer-Tropsch process exhibits self-sustaining oscillations that alternate between high and low activity states.
This insight published in the journal scienceopens the possibility of optimizing the reaction rate and increasing the yield of the desired product, which could lead to more efficient fuel production in the future.
“Velocity fluctuations, usually accompanied by large fluctuations in temperature, are undesirable in the chemical industry due to safety concerns,” said corresponding author Professor Norbert Kruse of the WSU Jean and Linda Voiland School of Chemical Engineering and Bioengineering. (corresponding author) said. “In this case, the oscillations are controlled and mechanistically well understood. With this foundation of understanding, both experimental and theoretical approaches to research and development can be quite different. It really becomes a knowledge-based approach, which is very useful for us.”
Rethinking catalyst design
The Fischer-Tropsch process is commonly used to make fuels and chemicals, but researchers have had little understanding of how the complex catalytic conversion process works. This process uses a catalyst to convert two simple molecules, hydrogen and carbon monoxide, into long chains of molecules, hydrocarbons that are widely used in everyday life.
Research and development in the fuel and chemical industries has used a trial-and-error approach for more than a century, but researchers will now design catalysts more intentionally and use vibrational techniques to tune reactions and improve catalytic reactions. will be able to cause the condition. performance.
The researchers first encountered this oscillation after graduate student Rui Zhang approached Kruse about the problem of not being able to stabilize the reaction temperature. Studying it together, they discovered surprising vibrations.
“It was very interesting,” Kruse said. “He showed it to me and I said, ‘Louis, congratulations, you have a vibration! “And we continued to develop this story.”
The researchers not only discovered that the reaction causes an oscillatory reaction state, but also discovered why this happens. That is, as the reaction temperature increases due to heat generation, the reaction gas loses contact with the catalyst surface, slowing the reaction and decreasing the temperature. When the temperature is low enough, the concentration of reactant gases on the catalyst surface increases and the reaction rate accelerates again. As a result, the temperature increases and the cycle ends.
Fusion of theory and experiment
For this study, the researchers demonstrated the reaction in the lab using a frequently used cobalt catalyst modified by the addition of cerium oxide and modeled how it works.Co-author Pierre Gaspard of the Free University of Brussels developed the reaction scheme and theoretically imposed Change the temperature periodically to reproduce the experimental rate and selectivity of the reaction.
“This is so beautiful that we were able to model it theoretically,” said corresponding author Yong Wang, Regents Professor in the WSU Boyland School and Zhang’s co-supervisor. . “Theoretical and experimental data were in close agreement.”
Kruse has been researching vibrational responses for more than 30 years. The discovery of oscillatory behavior due to the Fischer-Tropsch reaction was quite surprising because the Fischer-Tropsch reaction is mechanistically very complex.
“In our research, we sometimes experience a lot of frustration because things don’t go our way, but sometimes we have moments that we can’t explain,” Kruse said. “It’s very rewarding, but ‘rewarding’ is a weak word to describe the excitement of making this great progress.”
Reference: “Obcillating Fischer-Tropsch Reaction” by Rui Zhang, Yong Wang, Pierre Gaspard, Norbert Kruse, October 5, 2023, science.
DOI: 10.1126/science.adh8463
This research was supported by Chambroad Chemical Industry Research Institute Co., Ltd., the National Science Foundation, and the Department of Energy’s Basic Energy Sciences Catalysis Science Program.
