Sulfided red mud (a by-project in the production of alumina by the Bayer process) has been shown to be active as a catalyst in hydrodechlorination reactions. In order to evaluate the feasibility of red mud in industrial processes, which would be most interesting as the cost of this material is much lower than that of commercial catalysts, its deactivation must be characterised. In this study, the deactivation of sulfided red mud as a catalyst for the hydrodechlorination of tetrachloroethylene at 100 bar and 350 degreesC was studied. The variation of conversion with reaction time was determined in the presence and absence of carbon sulfide in the feed, a notorious increase in the catalyst life being observed in the presence of carbon sulfide. Fresh and used catalysts were characterised by nitrogen adsorption, X-ray diffraction, scanning electron microscopy and X-ray dispersion spectrometry. An increase in the specific surface and chlorine surface concentration of the catalyst and a decrease in sulphur surface concentration were observed, as well as crystallographic changes in iron species. (C) 2001 Elsevier Science B.V. All rights reserved.