Promotion of Selectivity to Propene in Mg3V2O8 Catalysts by Oxygen Spillover in the Oxidative Dehydrogenation of Propane

Abstract

The main objective of this work is to demonstrate that spill-over oxygen, Oso, promotes the selectivity to propene on Mg3V2O8 during ODP via a remote control mechanism (RCM). Catalysts were prepared by a) mechanical mixtures of Mg3V2O8+alpha-Sb2O4, b) calcining the mixtures at 873 K for 6 days and and c) by mechanical mixtures of Mg3V2O8+alpha-Mg2V2O7 A detailed physicochemical characterization (BET, XRD, XPS, TEM, AEM) of the solid state properties reveals that neither mutual contamination nor formation of a new phase occurs during catalytic reaction or calcination. alpha-Sb2O4 is inert in the reaction. Significant synergetic effects were observed in the mixtures: Mg3V2O8+alpha-Sb2O4 exhibit an increase of selectivity by suppression of unselective reactions. Mg3V2O8+alpha-Mg2V2O7 mixtures exhibit an increase in the conversion, yield and selectivity and a decrease in the CO2 formation. The role of Oso, which is produced by alpha-Sb2O4, would be that of inhibiting the non-selective sites. Oso is crucial in determining the catalytic properties of the magnesium vanadate catalyst. The existence of a cooperation via Oso between alpha-Mg2V2O7 and Mg3V2O8 could explain the discrepancies observed in the literature concerning the activity and selectivity of the pyre and ortho phases.