Layered double hydroxide-derived vanadium catalysts for oxidative dehydrogenation of propane: Influence of interlayer-doping versus layer-doping

Mixed-oxide vanadium catalysts for oxidative dehydrogenation (ODH) of propane have been prepared by thermal decomposition of Mg, Al-layered double hydroxides (LDHs) containing vanadium either in the brucite layer or in the interlayer. The materials have been characterised by XRD, ICP-AES chemical analysis, XPS, BET and ESR. The catalytic performance of the samples depended on the manner of incorporation of the vanadium into the LDH structure. The sample obtained from interlayer-doped precursor was more active and more selective than mixed oxides obtained from layer-doped LDHs. The difference in the catalytic properties was attributed to the different magnesium vanadates nucleating in the calcined samples, the pyrovanadate formed from the interlayer-doped LDH giving better performance than ortho-vanadate crystallising from the layer-doped precursor. It has been suggested that one of the factors contributing to the difference in the behaviour of both types of catalysts might be the difference in the covalency of V---O in-plane bonds around the reduced V centres.