Comparison of the structure of supported molybdenum oxide and tungsten oxide catalysts

In this paper some structural aspects of MoO3 and WO3 supported on "Y-AI2O3 and SiO3 are described. The catalysts are prepared by dry or wet impregnation. The influence of the nature of the support. concentration of the transition metal and preparation technique on the structure of the catalysts has been studied by Raman spectroscopy, x-ray diffraction and Temperature Programmed Reduction (TPR). Raman spectra strongly suggest the presence of octahedral surface molybdate and tungstate and bulk molybdenum trioxide and IUngslen trioxide. In addition a not yet identified molybdenum compound having a Raman band at 860 cm-1 is observed. From TPR on MoO3/y-Al2O3 and MoO3/ SiO2 it is plausible, that in both systems at least three molybdenum compounds are present. Based on the combined results of TPR and Raman spectroscopy a quantitative description of the molybdenum containing catalysts is presented