Preparation of AuPd/ZnO–CuO for the directional oxidation of glycerol to DHA

Abstract

Selective activation of the C–O bond of glycerol is a considerable challenge in current academic research. Herein, we fabricate an efficient AuPd/ZnO–CuO catalyst via a simple precipitation method and use it in the selective oxidation of glycerol (GLY) to produce dihydroxyacetone (DHA). Under base-free conditions, the AuPd/ZnO–CuO catalyst exhibits preferable catalytic performance compared with AuPd/ZnO and AuPd/CuO. The turnover frequency (TOF) of AuPd/ZnO–CuO reaches 687.1 h⁻¹, which is 25 times that of AuPd/CuO and 6 times that of AuPd/ZnO. The AuPd/ZnO–CuO catalyst also shows good selectivity toward DHA and the highest DHA yield of 65.3%, which is at the top level among the reported results. Through STEM-EDS, XRD and Raman analyses, we find that ZnO–CuO is a composite oxide and that Zn and Cu elements in the ZnO–CuO support are uniformly distributed. Furthermore, HRTEM, EPR, and XPS results show that AuPd/ZnO–CuO has smaller AuPd alloy nanoparticles (NPs) but a higher concentration of surface defect sites compared with AuPd/ZnO and AuPd/CuO. Together with the catalytic performance and feasible mechanism, we consider that the enhanced performance of the AuPd/ZnO–CuO catalyst could be mainly ascribed to the rich surface defect sites, which facilitate the adsorption and activation of the secondary hydroxyl groups of glycerol.