Ammoxidation of alkylaromatics over V 2O 5/TiO 2 catalysts

Abstract

V 2O 5/TiO 2 (anatase) catalysts prepared by the coprecipitation technique were tested in the reaction of alkylaromatics ammoxidation to the corresponding nitriles. The main factors influencing the selectivity were the ammonia partial pressure and the amount of vanadia in the catalyst. NH 3 was found to inhibit the overall reactant conversion relative to its oxidation. Moreover, ammonia stabilizes the intermediate of alkylaromatic activation, avoiding its combustion. At high hydrocarbon conversion, high degrees of ammonia combustion led to a decrease of the selectivity. The best catalytic performance was obtained with amounts of vanadia corresponding to the formation of a monolayer coverage of the anatase surface. For higher V 2O 5 content a strong increase of NH 3 combustion led to decrease of the nitrile yield. The catalysts were found to be active and selective in the ammoxidation of toluene, p- and m-xylene and o-chlorotoluene.