Highly Accessible, Stable and Active Sn Catalysis in Partially Dealuminated Beta Zeolites

Abstract

Sn-beta zeolite is a powerful Lewis acid catalyst. Recently it was shown that this material shows great activity and stability in carbohydrate-related conversions in water and other solvents. Among these reactions are isomerization of sugars and retro-aldol reactions yielding alkyl lactates, both essential steps in a carbohydrate-based renewable feedstock. Unfortunately, the synthesis of this catalyst is not straightforward. Long hydrothermal synthesis times are needed and the use of corrosive hydrogen fluoride is unavoidable. We present a simple way to synthesize a Sn-containing zeolite by grafting affordable Sn-species onto partially dealuminated beta zeolites. The presence of aluminum results in Brønsted acidity, the presence of tin yields Lewis acidity. This synthesis method allows to synthesize the Sn-beta zeolite in a couple of hours, with tunable parameters an without the use of hydrogen fluoride. The catalytic activity of the catalyst was tested in different reactions, and compared to the traditional synthesized Snβ. Catalysts synthesized by the grafting procedure show very high activities for all the tested reactions, with turnover frequencies per Sn much higher than the original Snβ.status: publishe