Effect of vanadium oxide loading on the selective oxidation of methane over vanadium oxide (V2O5)/silica

The effect of vanadium oxide loading on the selective methane oxidation over V[sub 2]O[sub 5]/SiO[sub 2] catalysts was investigated. X-ray diffraction (XRD) and temperature-programmed reduction (TPR) were used to characterize these catalysts. The results of XRD and TPR show that the catalysts with 1-8 wt% vanadium oxide loadings had a uniform structure but no well-defined crystalline phase of vanadium oxide. These catalysts showed very different selectivities for methanol. At the fixed methane conversion, methanol selectivity generally increased with the decrease of the vanadium oxide loading. The size of vanadium oxide ensembles may have significant effect on catalytic selectivity. N[sub 2]O was found to be much more active than O[sub 2] for the oxidation of methane. In the presence of both N[sub 2]O and O[sub 2], N[sub 2]O had to compete with O[sub 2] for the adsorption sites.