Catalytic Oppenauer oxidation of secondary alcohols over post-synthesized Sn-Beta

Abstract

Oppenauer oxidation is a promising strategy for oxidation of alcohols to carbonyl compounds, which is chemoselective and one of the useful tools in organic synthesis. Sn-Beta zeolite has shown promising and attractive performance in the Oppenauer oxidation of secondary alcohols as reductants. In this work, a set of Sn-Beta catalysts were successfully prepared by a facile post-synthesis method involving dealumination and Sn incorporation. The effect of Sn content on the catalytic performance was investigated in the selective oxidation of 1-methoxy-2-propanol (MOP) into methoxyacetone (MOA). The as-obtained 2Sn-Beta with 2 wt% Sn can afford an optimal performance with a MOP conversion of 63.3% and a MOA yield of 58.2% (91.9% selectivity) at 120 °C and using acetone as a H-acceptor. Based on a combination of advanced spectroscopic characterization and structure–performance correlation, we found that open framework Sn sites exhibit a much higher activity compared with other Lewis acid counterparts, for example, closed framework Sn and extraframework Sn sites. Our findings can be of help when looking to design efficient catalysts that can deliver improved performance for chemoselective oxidation of secondary alcohols and beyond.