One-pot synthesis of V doped mesoporous SiO 2 catalysts for selective oxidation of ethane and propane

摘要

A series of vanadium-doped mesoporous SiO2 catalysts were prepared using a one-pot emulsion method. The effects of VOx species with different structures on C-H bond activation and product selectivity in ethane and propane selective oxidation were investigated using X-ray diffraction (XRD), N-2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), hydrogen temperature programmed reduction (H-2-TPR), and ammonia temperature programmed desorption (NH3-TPD) characterizations. The results revealed that the highly dispersed isolated tetrahedral VOx species on the catalyst gradually polymerized into highly dispersed oligomeric VOx species with the increased V loading. The former is beneficial for the formation of olefins and total aldehydes during the selective oxidation of propane. Oligomeric VOx species are conducive to improving the selectivity of ethylene and acetaldehyde in the selective oxidation of ethane. The highest catalytic performances for selective oxidation of ethane and propane were obtained at a temperature of 650 & DEG;C. The conversion of ethane was 41.6 %, with a corresponding yield of ethylene and acetaldehyde of 23.6 % over a 0.5 V-SiO2 catalyst. In contrast, the propane conversion was 61.5 %, with a corresponding total yield of olefins and aldehydes of 41.3 % over a 1.0 V-SiO2 catalyst.