Hydrodehalogenation with sonochemically prepared Mo₂C and W ₂C

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 > C ₆H₅Cl > C₆H₅Br > C ₆H₅I. 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.