The effect of the bimetallic Pd-Pb structures on direct oxidative esterification of methacrolein with methanol

Supported palladium and palladium alloy were proved to be active catalysts for the oxidative esterification reaction of methacrolein with methonal to methyl methacrylate. Here we synthesized two types of structurally supported palladium alloy catalysts with ordered or disordered Pd3Pb intermetallic crystals by impregnationreduction method as well as high temperature heat treatment. Importantly, the catalyst with disordered Pd3Pb crystals had 89% conversion for methylacrolein and 79% selectivity for methyl methacrylate, showing obvious higher activity than the catalyst with ordered Pd3Pb crystals. The morphology, metal arrangement and electron effect of the catalyst were analyzed by XRD, TEM and XPS. It was confirmed that more active sites and strong electron transfer between metals were the reasons for the excellent performance of the disordered catalyst. This study provides theoretical guidance for the further study of Pd-based catalysts for the oxidative esterification of methacrolein to methyl methacrylate