Selective Oxidation Performance of Propane over Supported Vanadium Oxide Catalysts

Abstract

A series of SBA-15 supported vanadium oxide catalysts with different active components were prepared by the method of incipient-wet impregnation. The structures of the catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), ultraviolet (UV)-Raman, Fourier transform infrared (FTIR), and ultraviolet-visble diffuse reflectance spectroscopy (UV-Vis DRS) techniques, and their catalytic performances for the selective oxidation of propane were investigated. The results showed that SBA-15 was a better support in the catalyst system than SiO2 for the selective oxidation of propane to aldehydes. The SBA-15 supported low loading catalyst is a highly dispersed catalyst system and the SBA-15 supported vanadium oxide samples with low loading (n(V)/n(Si)<2.5%) have ordered hexagonal mesostructures. For the VOx/SBA-15 catalysts, isolated vanadyl species with tetrahedral coordination are the active sites for aldehyde formation at very low loadings of vanadium (n(V)/n(Si)<0.1%). The polymeric vanadyl species with octahedral coordination and microcrystalline vanadium oxide are active sites for the oxidative dehydrogenation or deep oxidation of propane when the loading of vanadium (n(V)/n(Si)) is higher than 2.5%.