Dechlorination of chlorobenzene in subcritical water with Fe/ZrO2, Ni/ZrO2 and Cu/ZrO2

Abstract

To obtain information about dechlorination of organochlorine compounds in subcritical water catalyzed by metals assisted with ZrO₂, dechlorination of chlorobenzene has been investigated in the presence of Fe/ZrO₂, Ni/ZrO₂ and Cu/ZrO₂catalysts. The dechlorination efficiency was increased with increasing residence time, temperature and pressure. The order of effectiveness of the catalysts was Cu/ZrO₂ < Ni/ZrO₂ < Fe/ZrO₂. The dechlorination of chlorobenze obeyed pseudo-first-order kinetics models. The rate constants in subcritical water were much greater than that in ambient-temperature water; the activation energies were obtained. ZrO₂ in the catalyst had the power to absorb chlorobenzene onto the catalyst surface and promoted the dechlorination ability of the metal. The primary mechanism for dechlorinaton of chlorobenzene involved the reduction of chlorobenzene by reaction with nascent hydrogen. The nascent hydrogen reacted with the chlorobenzene, which adsorbed on the catalyst in non-planar and co-planar form, and formed benzene and chloride ions.