visual image

News & Publications

Smit’s computational innovations help find new zeolite catalysts

Berend Smit
Berend Smit

March 04, 2008

Many of the substances that we take for granted everyday, from gasoline to plastics, have passed through the microscopic pores of zeolite catalysts during their production. But until recently, researchers could only speculate about what happens inside these catalysts and guess at how to use these catalysts effectively. But now, thanks to their pioneering computational techniques, two chemical engineers are finding new uses for zeolites to improve efficiency and reduce waste in the refining and petrochemical industry.

UC Berkeley chemical engineering and chemistry professor Berend Smit and Theo L. M. Maesen, a research scientist with Chevron Corporation, have developed sophisticated computational techniques to model zeolite-based catalytic processes. Their results have been published in a review article in the February 7 issue of Nature magazine.

Zeolites are microporous hydrated alumnosilicate materials. They have found wide use in industry since the late 1950s, especially as catalysts in the petrochemical industry. Zeolite catalysts break the long-chain hydrocarbons in crude oil into smaller molecules. In addition, these catalysts create the branched hydrocarbon isomers that are added to gasoline to improve its octane rating and to help it burn efficiently.

“Theo and I published our first paper in Nature on zeolites and computational techniques in 1995,” says Smit. “We committed ourselves then to improving computational techniques to the point that we could predict the catalytic behavior of zeolites via computer models.”

Although the first molecular dynamic simulation of molecules absorbed in zeolites took place about 20 years ago, the simulation was based on methane, a very simple hydrocarbon. Computers and techniques available then would have required millions of years to model how more complicated hydrocarbon chains diffuse and are shaped inside zeolites. Smit and Maesen have been able to speed the computations by using what they call a “free-energy landscape approach” that strips the catalytic processes down to their most basic thermodynamic roots. Then they apply a computational technique called configurational-bias Monte Carlo. The combination is at least a trillion times faster than conventional techniques.

So far, Smit and Maesen have applied their techniques to new uses for known zeolites. But, says Smit, “There are about 180 zeolite structures known to exist out of more than 1.5 million that are feasible on theoretical grounds. Computational techniques could be used to screen the hypothetical ‘designer catalysts’ even before we learn how to produce them, and then help in their construction.”

“When zeolite catalysts first were used in the petrochemical industry during the 1950s, they made huge impact on energy efficiency, says Maesen. “We need to continue to find new catalysts to help improve efficiency even more.” “Access to conventional crude oil stocks is declining,” Smit adds, “and with the arrival of alternative feed stocks from biological and other sources, there will be a growing demand to rapidly find new catalysts. We hope our computational techniques will play a role in identifying and screening the catalysts necessary for a more energy-efficient world.”

[top of page]