Influence of the Preparation Methods of V-Mg-O Catalysts on Their Catalytic Properties for the Oxidative Dehydrogenation of Propane

The influence of the preparation methods of V-Mg-O catalysts on their catalytic properties in the oxidative dehydrogenation of propane has been studied. By using MgO with surface areas from 49 to 141 m2 g−1 as supports, and carrying out the incorporation of vanadium starting from vanadyl oxalate or ammonium metavanadate, it has been found that different V species are formed, with V/Mg ratios at the catalyst surface ranging from 0.02 to 0.5. A new preparation procedure which allows a homogeneous dispersion of vanadium along the MgO is presented. The highest activity and selectivity are obtained on catalysts with an Mg-enriched surface in which isolated VO4 tetrahedra are present. Similar trends for the influence of the V/Mg surface atomic ratio on the selectivity to propene and for the shift of the binding energy (B.E.) of the O1s line, obtained by XPS, are observed. The higher the shift of the B.E. of the O1s line, the higher the selectivity to propene. For this reason, a correlation between the low nucleophilic character of the oxygen and the selectivity for the ODH of alkanes has been tentatively proposed.