Theoretical mechanistic insights into propylene epoxidation on Au-based catalysts: Surface O versus OOH as oxidizing agents

Abstract

Propylene oxide (PO) is an important bulk chemical used for synthesis of many value-added products. Much effort has been devoted to finding a simple and “green” process for PO production. Promising results in terms of activity and selectivity have been achieved for propylene oxidation on supported gold catalysts with a mixture of O2 and H2 or with O2 and H2O. In this work a detailed transformation network of competitive reaction pathways following the initial steps of oxidation has been studied theoretically using density functional theory (DFT). The results of calculations question some of the earlier assumptions regarding the mechanism of PO formation. Surface hydroperoxo species (OOH) formed in situ are shown to be responsible for the high selectivity of propylene epoxidation with O2 on gold-based catalysts using hydrogen or water as co-reactants.