V/Al/O oxides have been prepared and tested as catalysts for the ammoxidation of propane into acrilonitrile at 500 degrees C. The high efficiency of these catalysts, which were partially nitrided under catalytic reaction conditions, is confirmed. The best catalysts characterized by a V/Al ratio around 0.30, exhibited selectivity to acrilonitrile of 51% at 58% conversion. Testing at low conversion showed that propene was the main primary product from propane ammoxidation and that the reaction pathway on these catalysts was similar to that on other efficient catalytic systems. A new method of synthesis based upon the decomposition at low temperature of a mixed ammonium aluminum-vanadium oxalate was developed. It leads to highly active catalysts, which displayed increased selectivity to acrylonitrile. The gain in activity and selectivity was attributed to a better dispersion of vanadium with a higher concentration of isolated vanadium species in the bulk and presumably at the surface of the catalysts. (c) 2011 Elsevier B.V. All rights reserved.