Influence of MoO3 and WO3 on the dispersion and activity of V2O5 in vanadia-silica catalysts

Abstract

A series of silica-supported vanadia and molybdenum- and tungsten-promoted vanadia catalysts have been prepared and were characterized by means of low temperature oxygen chemisorption, 1H magic angle spinning nuclear magnetic resonance, X-ray diffraction, and electron spin resonance techniques. Reactivities of these catalysts for partial oxidation of methanol were also determined under atmospheric pressure in a flow microreactor. These results suggest the formation of the “patchy monolayer” phase of V oxide at lower loadings and on top of it bulk V2O5 at higher vanadium loadings. The presence of molybdenum increases the activity of the catalyst, whereas tungsten has the opposite effect. The improved activity of molybdena-vanadia catalyst was related to the better dispersion of the V oxide phase in the presence of Mo on silica surface