Liquid Phase Catalytic Hydrodechlorination of Chlorobenzene Under Microwave Irradiation

摘要

Heterogeneous catalytic dehydrochlorination of chlorobenzene by protons transfer was studied in a solution of NaOH in 2-propanol in the presence of a commercial alumina-supported Palladium (5 wt%) catalyst. Heating of the reaction mixture to the reflux temperature, ～83℃ was done by conventional methods (electric heating) and by microwave irradiation. It was established that microwaves had a strong effect on the catalytic process from point of view of both the reaction rate and activity of the catalyst — Fig. 5. Despite of the gradual decrease of the catalytic activity due probably to the formation of HCl and accumulation of NaCl on the surface of the catalyst, this decrease was just slightly observed in the microwave conditions. This observation is very important and it can be explained by either accepting material-wave interactions leading to thermal effects (connected to dipolar and charge space polarizations) and specific (non-purely thermal) effects resulting from variations in activations parameters, enhancements in molecular impacts and possibly high localized microscopic temperatures. The presence of 5 -12% of water in the catalyst has a positive effect on the reaction rate in the presence of microwaves.