Influence of reducibility of vanadium–magnesium mixed oxides on the oxidative dehydrogenation of propane

A series of vanadium–magnesium mixed oxides used for the propane oxidative dehydrogenation were synthesized by combining the impregnation and precipitation methods. Several techniques such as, FTIR, XRD and TPR-H2 were applied to characterize physicochemical properties. XRD analysis confirms that the V–Mg–O oxides consist of Mg3V2O8 structure with VO4 tetrahedral units together with periclase phase. Magnesium incorporation with vanadium inhibits the formation of V2O5 containing exposed Vdouble bond; length as m-dashO bonds. TPR-H2 results show two peaks located between 500 and 750 °C, which, respectively, correspond to reduction of V5+ species in distorted VO4 units and V5+ species belonging to bulk Mg orthovanadate. The highest activity and selectivity were obtained on catalysts in which isolated VO4 tetrahedral are present. A relationship between reducibility degree of V5+ distorted species (into unities VO4), and catalytic activity was observed. In order to get a higher activity a maximum content of 45% as vanadium oxide.