Characterization and catalytic behavior of VOx-CeO2 catalysts for the oxidative dehydrogenation of propane

A series of ceria-supported vanadium catalysts was prepared via impregnation of the support with an ammonium metavanadate solution. The 723 K calcined samples were tested for propane oxydehydrogenation (ODH) activity and selectivity. The sample exhibiting the highest propane conversion was found to be the ceria support material itself, although this showed essentially no selectivity towards propene. An optimum propene yield of 4.2% was obtained at 673 K for the 6 wt% V2O5-CeO2 sample. Conversion decreased with increasing V loading which was attributed to the formation of cerium vanadate (CeVO4). This phase was found in all samples after calcination, its abundance rising in proportion to the V loading. In the 6 wt% V2O5 catalyst hydrated surface VOx species were present, although they underwent conversion to CeVO4 at temperatures above 573 K. The low reducibility of these surface vanadates was linked to the oxidation activity. It is inferred that surface polyvanadate species are responsible for the selective ODH of propane with V-O-V and/or V-O-Ce being the active oxygen species.