Scientists Unveil Surprising Secrets of a 40-Year-Old Catalyst

3D model of the active center of the catalyst Titanium Silicalite -1 with the titanium pair (light grey).
Credit: ETH Zürich

Activity of the industrial catalyst TS-1 relies on titanium pairs/Important discovery for catalyst development.

‘Titanium silicalite-1’ (TS-1) is not a new catalyst: It has been almost 40 years since its development and the discovery of its ability to convert propylene into propylene oxide, an important basic chemical in the chemical industry. Now, by combining various methods, a team of scientists from ETH Zurich, the University of Cologne, the Fritz Haber Institute and BASF has unveiled the surprising mechanism of action of this catalyst. From Cologne, the working group of Professor Dr. Albrecht Berkessel at the Department of Chemistry was involved. These findings will help catalyst research take an important step forward.

Propylene oxide is used in industry to make products such as polyurethanes, antifreeze additives and hydraulic fluids. More than 11 million metric tons of propylene oxide are produced annually in the chemical industry worldwide, of which 1 million metric tons are already produced by the oxidation of propylene with hydrogen peroxide. This chemical reaction is catalyzed by TS-1, a microporous, crystalline material made up of silicon and oxygen and containing small amounts of titanium. The catalyst has been used successfully for 40 years and experts assumed that the active center in TS-1 contains individual, isolated titanium atoms that ensure the special reactivity of the catalyst.

A team of researchers from the ETH Zurich, the University of Cologne, the Fritz Haber Institute and BASF questioned this assumption. “In recent years, doubts have arisen as to whether the assumption about the mechanism of action is correct, as it relies primarily on analogies with comparable catalysts and less on experimental evidence. But if you try to optimize a catalyst on the basis of a wrong assumption, it is very difficult and can lead you in the completely wrong direction. It was therefore important to examine this assumption more closely,” explains BASF scientist Dr. Henrique Teles, one of the co-authors of the scientific publication, the starting point for the collaboration.

In a study now published in Nature, the team…

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