Efficient selective oxidation of propylene by dioxygen on mesoporous-silica-nanoparticle-supported nanosized copper

A direct synthetic route was developed to prepare mesoporous-silica-nanoparticle-supported copper catalysts featuring ordered mesostructures with extensive intraparticle voids, a high degree of silica condensation, and a high dispersion of copper species. After hydrogen reduction, the catalysts containing nanosized metallic copper showed superior and stable catalytic activity for the selective oxidation of propylene by dioxygen, with high conversion of both reactants and high yield and formation rate of acrolein. The best catalyst outperformed the state-of-the-art silica-supported copper catalysts, representing one of the most active acrolein-production catalysts. Results of in situ X-ray absorption spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy, and other characterizations suggested that the metallic copper transformed and mainly stayed in the 1+ oxidation state under reaction conditions and that factors including the small size of copper and the presence of silanol groups on the silica support were crucial for the catalytic performance of the catalysts.