Hydrodehalogenation with sonochemically prepared Mo2C and W2C

The catalytic hydrodehalogenation (HDH) of several halogenated organic compounds was performed over sonochemically prepared molybdenum carbide and tungsten carbide at low temperatures (T = 200-300 degreesC). Both catalysts were selective, active, and stable for all substrates tested. Benzene was observed as the major product for the HDH of fluoro-, chloro-, bromo- and iodobenzene, with activities following the trend of C6H5F > C6H5Cl > C6H5Br > C6H5I. For the HDH of chlorofluorocarbons (CFCs), Cl was selectively removed over F and alkanes were the major product. In the liquid phase, the HDH of polychlorinated and polybrominated biphenyls resulted in biphenyl as the only product. The HDH of substrates bearing aliphatic C-Cl bonds occurs faster than those with arene C-Cl bonds. Time-on-stream studies of HDH of chlorobenzene show high stability for the sonochemically prepared catalysts, with half-lives as long as 600 h. (C) 2003 Elsevier B.V. All rights reserved.