Kinetics and Mechanisms in the Ammoxidation of Toluene over a Titania TiO2(B)-Supported Vanadium Oxide Monolayer Catalyst. 1. Selective Reactions

A kinetic investigation of the ammoxidation of toluene was carried out over a TiO,(B)-supported vanadium oxide catalyst with a loading corresponding to a theoretical monolayer. The partial pressures of reactants toluene, oxygen, and ammonia were varied, and rates were measured for the formations of benzaldehyde and benzonitrile. By analysis of the rate dependencies on partial pressures of reactants, rate expressions completely describing the data were derived. These show that benzaldehyde is formed from two routes in which the. active ensemble accommodates one and two toluene molecules, respectively. The latter route is most facile. For the formation of benzonitrile, there are also two routes. In the route that is major at low partial pressures of ammonia, one ammonia molecule is adsorbed. With increase in the partial pressure of ammonia, a second route involving adsorption of two ammonia molecules at the active ensemble becomes increasingly important.