Taking a cue from nature

October 30, 2013

It's not unusual for scientists to take their cues from nature. In fact, Jeff Rimer is building much of his career on such cues.

Rimer, an assistant professor of chemical and biomolecular engineering with the University of Houston Cullen College of Engineering, is an expert in the field of crystallization. The processes behind crystal growth and formation impact everything from drug development to chemical synthesis to medical diseases such as kidney stones and malaria.

One of the primary efforts of Rimer's lab involves a class of crystals known as zeolites. These are widely used by the chemical and petrochemical sector as catalysts, which initiate or speed up chemical reactions. A material will diffuse through pores in a zeolite crystal, react with specific sites in the crystal interior, and then exit, transformed into a more useful chemical. Rimer is attempting to control how zeolites grow in order to make them more efficient catalysts for commercial reactions.

"The original work I performed with modified zeolite synthesis was inspired by processes in natural mineral formation," said Rimer. "Sponges and diatoms form amorphous silica exoskeletons. They possess elaborate hierarchical structures that are created through specific interactions with proteins."

Rimer, then, has identified and developed a number of molecules that, in a similar manner, alter the growth and shape of zeolites in order to optimize their catalytic properties. He has won multiple grants supporting this work (including a National Science Foundation CAREER Award), has published extensively on his findings and is even pursing a patent for a method to rationally design new zeolites.

Rimer's latest grant in this area comes from the United States-Israel Binational Science Foundation, an independent body formed though an agreement between the two countries. He and his collaborator, Galia Maayan from the Technion - Israel Institute of Technology (often called Israel's MIT), received a two-year, $150,000 award to develop a class of molecules called peptoids that will be designed to alter zeolite growth.

This latest grant covers zeolites that, when unmodified, are shaped like cylinders, with their pores running the length of the cylinder. Molecules that enter these pores must travel much farther than needed during the course of the reaction. As a result, the catalysts are more susceptible to the formation of coke, a carbon-rich deposit that blocks the pores and deactivates the catalyst.

Like all crystals, these zeolites grow when new molecules of the crystal material attach to specific locations (known as growth sites) on the zeolite surface. Rimer and Maayan are developing peptoids that bind to the zeolite surfaces at these sites. A segment of the peptoid will then physically block the growth sites, thus frustrating the attachment of additional molecules to the crystal.

By blocking these sites, he aims to change the shape of these zeolites from cylinders to flat platelets. This will significantly improve the lifetime of catalysts by reducing coke formation in various reactions. As a result companies should be able to carry out these processes more efficiently and for less money than before.

Just as importantly, using modified zeolites would require little to no changes in the manufacturing processes used by companies in the chemicals sector, said Rimer.

"This is something that could be integrated into an existing process very easily, without requiring equipment upgrades or dramatic changes in operating conditions," Rimer explained. "So from an economic perspective, this could be very attractive for industry."
-end-
By Toby Weber

University of Houston

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