A new catalyst for propane ammoxidation: the Sn/V/Sb mixed oxide

The effect of the preparation and calcination method of a Sn/V/Sb mixed oxide on its catalytic performance are analyzed with respect to ammoxidation of propane. Different samples have been prepared with coprecipitation technique (by dissolving the starting materials with ethanol, iso-butanol or water), or by solid state reaction between oxide and tin hydroxide. The sample prepared by ethanol shows the best catalytic performance: this solvent makes the partial alkoxides quite stable in solution and brings about a better coprecipitation with a more intimate mixture of tin, antimony and vanadium. The thermal transformation of the precursor of this sample has been followed during the calcination, both in air and in nitrogen with several characterization techniques. The thermal treatment in air at 700 degrees C leads to the best catalytic performance, that is, good activity and high selectivity. This calcination procedure leads to a homogenous mixed oxide, with numerous well-crystallized microfields of tin oxide, incorporating antimony and vanadium ions in limited concentrations and an excess of poorly crystallized antimony oxide.