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 degrees 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. (C) 2000 Elsevier Science B.V. All rights reserved.