Influence of the reaction conditions and catalytic properties on the liquid-phase hydrodechlorination of chlorobenzene over palladium-supported catalysts: Activity and deactivation

The liquid-phase hydrodechlorination of chlorobenzene with molecular hydrog en was studied over palladium-supported catalysts. The reaction takes place at a gradually decreasing rate through progressive poisoning of the active phase by chloride ions. It is found that the correct choice of the metalli c precursor (free of chloride ions) is crucial for the optimum performance of the final solid obtained. In addition, a better resistance to chlorine i s observed when the size of the metallic particle increases. The supports t ested, viz. SiO2/AlPO4, ZrO2, and MgO, significantly affected catalyst deac tivation, Thus, supports that can capture chloride species (e.g., ZrO2) all ow the reaction to finalise within relatively short times. The reaction app eared to be structure-sensitive in regard to the initial activity. Changing dispersion from 54 to 7% was accompanied by an increase in catalytic activ ity by a factor of 20. (C) 1999 Academic Press.