Activating molecular oxygen by Au/ZnO to selectively oxidize glycerol to dihydroxyacetone

Abstract

The activation of molecular oxygen is a critical step in gold-catalyzed aerobic oxidation of alcohols. In this paper, we demonstrate that the charge of Au-adsorbed oxygen as well as the length of the O–O bond provides a useful descriptor for predicting effective catalysts for glycerol oxidation under base-free conditions. ZnO was theoretically predicted and experimentally confirmed to be the most effective support for Au to activate molecular oxygen and thus to catalyze aerobic oxidation of glycerol. Kinetic studies as well as electron paramagnetic resonance (EPR) spectra indicate that the as-generated O₂⁻ species on the surface of Au/ZnO could selectively abstract protons from the central hydroxyl group of glycerol to form dihydroxyacetone (DHA), resulting in a selectivity to DHA of up to 85%.