An XPS study of La2O3 and In2O3 influence on the physicochemical properties of MoO3/TiO2 catalysts

Abstract

To explore the influence of La2O3 and In2O3 doped TiO2 support on the dispersion and chemical nature of Mo-oxide species an investigation was undertaken by using XPS and other techniques. In this study, the La2O3–TiO2 and the In2O3–TiO2 binary oxide supports were prepared by a homogeneous coprecipitation method with in situ generated ammonium hydroxide and were deposited with MoO3 by adopting a wet impregnation technique. The Mo-containing catalysts and the corresponding supports were characterized by means of XRD, FTIR, XPS, and BET surface area methods. Characterization results suggest that the calcined (773 K) La2O3–TiO2 and In2O3–TiO2 binary oxides are in X-ray amorphous state and exhibit reasonably high specific surface area. These supports also accommodate a monolayer equivalent of MoO3 (12 wt.%) in a highly dispersed state on the surface. Both La2O3 and In2O3 dopants show a strong influence on the electronic properties of the MoO3/TiO2 catalysts as evidenced by a change in the XPS binding energies of these metal oxides. The XPS binding energy values further indicate that the dispersed molybdenum oxide is in Mo(VI) oxidation-state. However, the maximum broadening of Mo 3d as observed from full width at half-maximum values indicates that the presence of different Mo(VI) species on both the support surfaces.