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 °C). 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.