Researchers expand ways to improve the selectivity of catalytic reactions

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), the Harvard Department of Chemistry and Chemical Biology, and Utrecht University have reported a novel method for improving the selectivity of catalytic reactions, in which A new addition method has been added. The usefulness of catalysts for a potentially wide range of applications in various industries including pharmaceuticals, cosmetics and more.

Published in research. Nature catalysis.

gave Chemical industry More than 90% of its processes rely on catalysts, and almost all of these catalysts consist of nanoparticles dispersed over a substrate. Researchers have long suspected that the size of individual nanoparticles and the distance between them play an important role in their speed and the products they produce. Catalytic reactionbut because nanoparticles tend to move around and aggregate during catalysis, it has been difficult to study how.

Over the past decade, Joanna Eisenberg, Amy Smith Berelson Professor of Materials Science and Professor of Chemistry and Chemical Biology, and her lab have taken inspiration from nature to create highly ordered, porous materials for a wide range of catalytic reactions. have been

Inspired by the structure of butterfly wings, the researchers designed a new one. actionable The platform partially embeds the nanoparticles into the substrate, trapping them so that they do not move around during catalysis, while leaving the surface of the rest of the nanoparticles exposed, allowing them to efficiently and without agglomeration of the catalyst. Enables the reaction to take place.

The researchers found that the distance between the particles has a large effect on the selectivity of the reaction.

“Many industrially relevant chemical reactions follow a cascade whereby chemical A is converted to chemical B, which is then can be converted into chemical C etc”. .

“In some catalytic processes, the intermediate chemical, chemical B, is the target, while in others it is the final product, chemical C. The selectivity of a catalyst refers to whether it favors the production of chemical B or chemical C. “

A good example is the production of benzyl alcohol, a chemical used in everything from the production of shellacs, paints, and leather to intravenous drugs, cosmetics, and topical medications.

Benzyl alcohol is an intermediate chemical B, derived from the hydrogenation of benzaldehyde (chemical A) before the reaction forms toluene (chemical C), another commonly used but less expensive chemical. To produce benzyl alcohol efficiently, the formation of toluene needs to be suppressed.

Currently, to make more efficient benzyl alcohol, the catalytic hydrogenation reaction is slowed down, or not run to completion, to ensure that the reaction stops at B and as little toluene as possible. will make

“Typically, to make these intermediate chemicals, you make the catalyst less reactive and the overall reaction slower, which is not productive at all,” Lim said. “Catalysts are meant to speed things up, not slow them down.”

The researchers demonstrated their platform in the catalytic formation of benzyl alcohol. Lim and team found that when the catalytic metal nanoparticles were placed further apart on the substrate, the reaction was more selective toward benzyl alcohol, the chemical intermediate.

When the nanoparticles were closer together, the reaction was more selective toward toluene, which is the final product. Given that the distance between nanoparticles can be artificially adjusted using a bio-inspired catalyst platform, research suggests that the same catalyst platform can be easily adapted to a range of intermediate or end-product chemicals. Can be adapted.

“Catalysis is central to the production of a whole range of critical materials that are used in pharmaceuticals, consumer products, and many other products that we all use in our daily lives,” Eisenberg said.

“Adding this selectivity-enhancing tool to the chemist’s arsenal is critical. It will allow more efficient tuning of catalytic processes, more economical use of feedstock with reduced energy consumption and waste generation. We We hope that chemists will use our platform in the further optimization of new and existing catalytic processes.”

Next, the team will use the same platform to understand how the size of the nanoparticles affects the response at fixed distances between them. Nanoparticles.

Harvard’s Office of Technology Development has protected intellectual property outside Professor Eisenberg’s laboratory, the technology underlying this research.

The study was co-authored by Selina K. Keizer, Haichao Wu, Sidhya Garg, Marta Praxis Perich, Jesse ES van der Hoeven and Michael Eisenberg.