Hydrodechlorination of chlorobenzenes on platinum (Pt)-supported-gamma-alumina and alumina Lewis superacid (AmLSA) catalysts was carried out at room temperature and ambient pressure using a fixed bed flow reactor and a semi-batch reactor. Both the catalysts indicated good activity for the hydrodechlorination, but the former was superior to the latter. The hydrodechlorinations of reactants C6H6-xClx (x = 1, 2, 3) proceeded step-wisely to benzene and then cyclohexane via C6H6-yCly (y = x - 1). The reactions seem to be promoted by the contribution of spillover hydrogen formed on the Pt-supported catalysts. The catalysts deactivated with reaction time and the amount of chlorine that accumulated on the Pt-supported gamma-alumina catalyst in the hydrodechlorination of 1,4-dichlorobenzene for 3 h was near to that estimated from the converted reactant molecules. When the deactivated catalysts were treated in a stream of hydrogen above 503 K, the original activity was completely restored, but the deactivation phenomenon with reaction time was observed again. (C) 2003 Elsevier B.V. All rights reserved.