Complete Hydroclechlorination of Chioro-Aromatics Catalyzed by Pd/TiO_2 with H_2

摘要

Pd/TiO_2 catalyzed rapid and complete hydrodechlorination of 2,4-dichloro-phenoxyacetic acid (2,4-D) dissolved in H_2O with H_2 to phenoxyacetic acid (PAA) at 303 K. Optimum reaction conditions were studied. The maximum turnover number of Pd for the dechlorination was 304 in 10 min at P(H_2)=1 atm and 348 K. The hydrodechlorination of 2,4-D to PAA proceeded by successive reaction through 2-chloro-phenoxyacetic acid (2-Cl-PAA) and 4-chloro-phenoxyacetic acid (4-Cl-PAA). The state of Pd after the hydrodechlorination was determined Pd~0 by XANES spectra. The hydrodechlorination should occur by nucleophilic substitution of Cl~- with active hydrogen species, such as H~-, generated at interface of Pd~0 and TiO_2.