The catalytic membrane reactor and the inert packed bed membrane reactor were studied in the vapour phase selective oxidation of toluene. Different feeding policies for the membrane were explored and their influence on the selectivity to the desired products (benzaldehyde and benzoic acid) was investigated. The active phase was prepared by depositing vanadium on a Al2O3-TiO2 Support prepared through the sol-gel technique. Higher selectivity to benzaldehyde was obtained using the catalytic membrane reactor. Differences were seen in the catalytic membrane reactor performance only when the active phase was heavily charged along the membrane cross-section. (c) 2004 Elsevier B.V. All rights reserved.