Preparation of H₃PMo₁₂O₄₀ catalyst immobilized on surface modified mesostructured cellular foam (SM-MCF) silica and its application to the ethanol conversion reaction

Surface of mesostructured cellular foam (MCF) silica was modified by grafting 3-aminopropyl-triethoxysilane (APTES) to have the positive charge, and thus, to provide sites for the immobilization of H₃PMo₁₂O₄₀. By taking advantage of the overall negative charge of [PMo₁₂O₄₀]^3-, H₃PMo₁₂O₄₀ catalyst was chemically immobilized on the aminopropyl group of surface modified MCF (SM-MCF) silica as a charge matching component. It was revealed that H₃PMo₁₂O₄₀ species were finely and molecularly dispersed on the SM-MCF silica via chemical immobilization. In the vapor-phase ethanol conversion reaction, the H₃PMo₁₂O₄₀/SM-MCF silica catalyst showed a higher ethanol conversion than the bulk H₃PMo₁₂O₄₀ catalyst. Furthermore, the H₃PMo₁₂O₄₀/SM-MCF silica catalyst exhibited an enhanced oxidation catalytic activity (formation of acetaldehyde) and a suppressed acid catalytic activity (formation of ethylene and diethylether) compared to the mother catalyst. The enhanced ethanol conversion and oxidation catalytic activity of H₃PMo₁₂O₄₀/SM-MCF silica catalyst was attributed to fine dispersion of H₃PMo₁₂O₄₀ species on the SM-MCF silica via chemical immobilization.