Effect of the preparation technique on the catalytic performances of TiO2 supported vanadium phosphate in the oxidative dehydrogenation of ethane

TiO2 supported VOPO4 catalysts, prepared by direct impregnation of TiO2 with VOPO4 or by dispersing a V2O5 precursor on previously phosphated titania, have been investigated for the oxidative dehydrogenation of ethane to ethylene at 823 K. The catalysts have been characterised with XRD, BET surface area measurements, XPS, TPR and NH3 TPD techniques. Preparation method influences surface composition of the sample, formation of V5+ oxide being favoured with respect to V4+ oxide for the catalyst prepared in two steps, whereas a comparable fraction of VOPO4 is formed on both samples. Results of catalytic tests suggests that the presence of V4+ strongly improves performances leading to higher ethylene yields.