Investigation of the oxidation of o-xylene over a vanadia/titania catalyst by means of the TAP reactor

The oxidation of o-xylene over a commercial V2O5/TiO2 (anatase) catalyst was studied in the TAP (Temporal Analysis of Products) reactor system. The transient method with high time resolution has led to new insights into the reaction mechanism. The selective oxidation is shown to consist of a sequence of steps, involving intermediates which desorb as o-toluolaldehyde and phtalide. The key reaction step in the non-selective oxidation is shown to be a decar-bonylation of a surface species, leading to a surface benzoate. The kinetics of the elementary steps in the reaction were derived from a quantitative analysis of the transient responses on o-xylene pulses. On a etudie l'oxydation du o-xylene sur un catalyseur commercial V2O5/TiO2 (anatase) dans un reacteur TAP (analyse temporelle de produits). La methode transitoire a haut taux de resolution permet de mieux comprendre le mecanisme de reaction. On montre que l'oxydation selective consiste en une sequence d'etapes, faisant intervenir des intermediaires qui desorbent come le o-toluolaldehyde et la phtalide. On montre egalement que l'etape de reaction cle dans l'oxydation non selective est la decarbonylation d'une espece de surface, menant au benzoate de surface. Les cinetiques des etapes elementaires dans la reaction ont ete calculees a partir d'une analyse quantitative des reponses transitoires de pul-sions de o-xylene.