USE OF ESCA VALENCE BANDS TO INFER STRUCTURAL INFORMATION ABOUT THE MOLYBDENUM PHASE IN SUPPORTED MOLYBDENUM CATALYSTS

X-ray photoelectron spectroscopy (XPS, ESCA) valence band spectra were used to infer information about the molybdenum phase in standard Mo compounds such as sodium molybdate and ammonium heptamolybdate and in Mo/Al2O3 catalysts prepared by equilibrium adsorption and incipient wetness impregnation methods. ESCA valence band measurements can distinguish between tetrahedrally coordinated Mo (sodium molybdate) and octahedrally coordinated Mo (ammonium molybdate). Mo ESCA valence band results show that Mo/Al2O3 catalysts prepared by equilibrium adsorption at pH 2.2 and Mo/Al2O3 catalysts prepared by incipient wetness impregnation contain primarily octahedral Mo.