Catalytic dechlorination of aromatic chlorides with noble-metal catalysts under mild conditions: approach to practical use

Catalytic dechlorination of aromatic chlorides was carried out in a solution of NaOH in 2-propanol with a carbon-supported Rh-based catalyst (Rh-Pt/C) at temperatures below 35°C. It was found that the dechlorination rate of aromatic chlorides (chlorobenzene, p-chlorotoluene, and 4-chlorobiphenyl) is strongly dependent upon the substituents. The dechlorination rate is hardly affected by the presence of water (ca. 10%), even under aerobic conditions, although the catalytic activity is suppressed significantly in the presence of acetone (ca. 5%). The catalyst life was evaluated both in a batch system and in a continuous-flow system. The catalytic activity gradually decreased, probably because of an accumulation of NaCl on the catalyst surface. The deactivated catalyst could be reactivated by washing it with water.