Epoxidation of trans-stilbene and cis-cyclooctene over mesoporous vanadium catalysts : support composition and pore structure effect

Vanadium supported on mesoporous molecular sieve catalysts with different pore diameters and structures (V-MCM-41, V-SBA-15, and V-TUD-1) were synthesized using a post-synthesis grafting method. The physicochemical properties of these as-calcined mesoporous vanadium catalysts were investigated by several techniques including N2-physisorption, X-ray diffraction, UV–vis, UV–Raman, and X-ray absorption near-edge structure spectroscopies. The characterization results revealed that the vanadium domains were mainly isolated VO4 units with a distorted tetrahedral coordination. Epoxidation of trans-stilbene and cis-cyclooctene were carried out to determine the influence of pore size and pore structure on the catalytic activity in a liquid-phase reaction. The best catalytic performance was achieved over the V-TUD-1 catalyst. It was suggested that the unique open 3D sponge-like mesostructure of the TUD-1 support can effectively suppress the pore diffusion resistance on bulky reactants and allow the good accessibility of reactants to the active sites embedded on the pore wall surfaces of mesoporous channels