Oxidative dehydrogenation of propane on vanadium supported on magnesium silicates

Sepiolite supported vanadium catalysts have been studied in the oxidative dehydrogenation of propane. Different vanadium species are present on the catalysts and the proportion changes with the preparation methods, support modifications, and vanadium content. At low vanadium content, isolated tetrahedral species are formed and both activity and selectivity to propene increase when increasing the vanadium content. At medium or high vanadium content the appearance of associated vanadium species can be observed and, while the activity still increases when increasing total vanadium, the selectivity to propene remains constant. MgV2O6 and V2O5 crystallites are formed at vanadium content higher than 30 wt.% of V2O5, and, depending on the propane conversion level, the selectivity to propene remains constant or decreases when increasing the vanadium content. On a comparative basis, the oxidative dehydrogenation of propane has also been carried out on a V2O5/MgO catalyst. From the comparison between catalytic properties in the oxidative dehydrogenation of propane on V/sepiolite and V/MgO catalysts a reaction network has been established and both type of catalysts show the same conversion-selectivity behaviour. The nature of the sites responsible for selective and non-selective oxidation on V/sepiolite catalysts has been proposed.