Comparative study on Al_2O_3 or SiO_2 supported vanadium oxides by UV-Raman spectrometry

Al2O3-or SiO2-supported vanadium oxide catalysts were prepared by citric acid-assisted incipient-wetness impregnation method,and their structures were characterized by UV-Raman spectrometry.The results indicated that the structure of supported vanadium catalysts was dependent on the vanadium loadings and types of the supports.At lower vanadium loadings,there existed isolated monovanadate species on the catalyst surface.At higher vanadium loading,VOx species existed as polyvanadate species and V2O5 on Al2O3,but vanadium existed predominantly as isolated monovanadate species and V2O5 with a little amount of polyvanadate species on SiO2.