V–Al–O catalysts prepared by flame pyrolysis for the oxidative dehydrogenation of propane to propylene

A flame pyrolysis (FP) procedure has been set up for the preparation of V/Al/O catalysts to be employed for the oxidative dehydrogenation of propane to propylene. The samples have been characterised by means of various techniques (FT-IR, Raman, EPR, ICP-MS, TGA, XRD, SEM) and their catalytic activity has been evaluated in two different operating modes, i.e. under anaerobic conditions and by co-feeding oxygen. The particle size distribution became progressively more homogeneous with increasing V concentration, due to the catalytic effect of the V ions during the FP synthesis. Some V2O5 segregation was observed even at low V loading. However, higher V dispersion was attained with respect to a reference sample prepared by impregnation of the FP-prepared alumina support. The increase of V concentration always led to an improvement of propane conversion, though selectivity showed different trends depending on the operating conditions. The comparison with the sample prepared by impregnation showed similar catalytic activity, with a bit higher selectivity for the FP-prepared sample under anaerobic conditions.