Selective Oxidation of Ethane over SBA-15 Mesoporous Zeolite Supported Vanadium-Based Oxide Catalysts

A series of SBA-15 supported vanadium oxide (V/SBA-15) and K-modified vanadium oxide (K-V/SBA15) catalysts with different active components were prepared by incipient-wetness impregnation. The structures of the catalysts were characterized using N-2 adsorption, low angle X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and UV-Raman spectroscopy techniques. Their catalytic performances for the selective oxidation of ethane were also investigated. The results showed that SBA-15 was a better support for the catalyst system than SiO2 for the selective oxidation of ethane to aldehydes. The SBA-15-supported low loading catalyst was a highly dispersed catalyst system and the SBA-15 supported K-V samples with low loading (n(v):n(Si) <= 5.0:100) had ordered hexagonal mesostructures. For the V/SBA-15 and K-V/SBA-15 catalysts, isolated vanadyl species with tetrahedral coordination are determined to be the active sites for aldehyde formation at very low vanadium loading (n(v):n(Si) <= 0.1:100). The polymeric vanadyl species with octahedral coordination and the microcrystalline vanadium oxide constitute the active sites for the oxidative dehydrogenation or deep oxidation of ethane when the loading of vanadium is higher than 2.5:100.