Insight into the Effect of Copper Substitution on the Catalytic Performance of LaCoO3-Based Catalysts for Direct Epoxidation of Propylene with Molecular Oxygen

Abstract

Direct epoxidation of propylene to propylene oxide (PO) with molecular oxygen as the most atomically economical route remains challenging due to the low PO yield. In this study, CuO supported on perovskites (LaCoO₃) modified with NaCl was found to be active for direct epoxidation of propylene with oxygen. LaCoₓCu₁–ₓO₃– modified with alkali metal salts were further fabricated to improve catalytic performance with the assistance of citric acid. Among the investigated catalysts, LaCo₀.₈Cu₀.₂O₃₋δ exhibited the best catalytic performance, with a PO formation rate of 60.4 gPO·kgcₐₜ⁻¹·h⁻¹ (PO selectivity of 10.2% and propylene conversion of 12.0%) at a lower temperature (250 °C). The characterization results indicate that Cu-doped LaCoO₃ catalysts with enhanced oxygen vacancies and abundant electrophilic oxygen species are crucial to selectively attack on C═C bond instead of C–H bond. Besides, LaCoₓCu₁–ₓO₃₋δ catalysts demonstrated higher propylene conversion and more stable catalytic performance. This work exemplifies the direct propylene epoxidation with molecular oxygen employing perovskite materials.