To investigate the role of vanadium oxide supported on mesoporous silica (VOx/m-SiO2) catalysts in methane oxidation to formaldehyde, various catalysts were prepared. The type of m-SiO2 (SBA-15 and MCF-17), vanadium loading (1, 3, and 5%), and preparation method (wet impregnation; WI and dry impregnation; DI) were changed to produce VOx/m-SiO2 with different vanadium species. Because of the larger surface area and pore size, a higher dispersion of vanadium loading, 1% VOx/MCF-17(DI), showed the highest conversion (20.2%) in methane oxidation at 600 oC. Various characterizations revealed that DI was a better method to produce isolated tetrahedral monovanadate species in VOx/m-SiO2 catalysts than WI. As the vanadium loading was decreased from 5 to 1%, the methane conversion was further increased due to the higher degree of dispersion of monomeric VO4 generated in the catalysts with low vanadium loading. The combined results demonstrate that the dispersion of vanadium and the isolated monomeric VO4 phase increased when the vanadium catalyst was loaded on MCF-17 and prepared by the DI method.
