Synthesis, characterization, and catalytic performances of potassium-modified molybdenum-incorporated KIT-6 mesoporous silica catalysts for the selective oxidation of propane to acrolein

Abstract

A series of novel molybdenum-incorporated mesoporous silica catalysts (Mo-KIT-6) were successfully synthesized by a one-pot co-assembly method. For comparison, corresponding mesoporous KIT-6-supported molybdena catalysts (Mo/KIT-6) were also prepared by the impregnation method. For Mo-KIT-6 catalysts, the molybdenum was substituted into the framework of the KIT-6 support, which contributed to obtaining high concentrations of highly dispersed and isolated active sites and to anchoring the active sites firmly. We determined the identity of the active sites of Mo-KIT-6 catalysts as Mo oxide units with more anchoring MoOSi bonds than in the corresponding Mo/KIT-6 at elevated temperature. The Mo-KIT-6 catalysts possess appropriate redox properties, high stability, and a strong ability to resist carbonaceous species formation, which was confirmed by in situ UV Raman results. Furthermore, the addition of K to Mo-KIT-6 catalyst further promoted the formation of acrolein, and the maximum single-pass yield of acrolein reached 25.9%.