To investigate the mechanism of the catalytic combustion of chlorobenzene over pure CeO2 and Ru doped CeO2 catalysts, we examined the oxidation reaction in depth by temperature-programmed surface reaction (TPSR) technique and a series of supplementary experiments. The results suggest that the C-Cl bond in chlorobenzene molecule can be dissociated easily on Ce3+/Ce4+ active sites, and the dissociated chlorobenzene can be rapidly oxidized into CO2 and H2O by surface reactive oxygen or lattice oxygen. The chlorine species dissociatively adsorbed on the active sites can result in the rapid deactivation of catalysts and be removed in form of Cl-2 via the Deacon Reaction catalyzed by RuO2 or CeO2, which would improve the catalyst stability. Additionally, the partial chlorination of RuO2 or CeO2 possibly occurs during the long reaction, which is responsible for the production of dichlorobenzene by-products. (C) 2012 Elsevier B.V. All rights reserved.