Copper-doped LaCoO3 for direct propylene epoxidation: a DFT study

Abstract

There are few reports on the direct epoxidation of propylene catalyzed by LaCoO₃ perovskite to form propylene oxide (PO) (both experimental and theoretical studies), especially the promoting effect of Cu doping. Herein, we report a comprehensive mechanistic study using both DFT calculations and microkinetic simulations for undoped and Cu-doped LaCoO₃(110)–Cl to explore the effects of Cu doping in LaCoO₃ perovskite towards PO selectivity. The propylene oxidation process consists of two parallel pathways, i.e., allylic hydrogen stripping and propylene oxametalcycle (OOMMP) intermediate mechanisms. Our results indicated that doping Cu has little effect on the selectivity for PO on LaCoO₃ without Cl due to its very low reactivity. Alternatively, in the presence of Cl, copper doping not only lowers the strength of the Brønsted base of molecular , and thus disfavors the propylene α-H striping process, leading to higher OOMMP intermediate formation selectivity, but also enhances the secondary chemistry, improving both the selectivity and activity for PO formation. Moreover, the microkinetic modelling results showed that the Cu-doped LaO-terminated LaCoO₃(110)–Cl surface has higher selectivity for PO than that of the Cu-doped CoO-terminated LaCoO₃(110)–Cl surface. It is hoped that the present work will help researchers better understand the mechanism of Cu doping in LaCoO₃-like perovskite catalysts for PO formation reactions.