Mechanical mixtures of Sb2O3 and V/Al/O mixed oxide have been tested as catalysts in the ammoxidation of propane. The results obtained showed that upon addition of Sb2O3 the propane conversion rate and the selectivity to acrylonitrile were decreased but to a limited extent whereas a strong decrease in selectivity to CO x was observed to the advantage of selectivity to propene. Sb2O3 completely reacts with the V/Al/O mixed oxide to form a rutile-type V1-xAlxSbO4 phase that spreads over the mixed oxide. If the structure modifications have to be taken into account to explain the difference in catalytic properties, the characterization of the catalysts allowed proposing that they primarily result from the contamination of the surface of the active V/Al/O mixed oxide by Sb species. If the changes in catalytic properties evidenced in the study appear rather unproductive in terms of yield in acrylonitrile, they can be of interest if a process integrated a recycling of the reaction feeds was designed for an industrial application. (C) 2013 Elsevier B.V. All rights reserved.