Improving the activity in hydrodechlorination of Pd/C catalysts by nitrogen doping of activated carbon supports

Abstract

Aqueous phase 4-chlorophenol hydrodechlorination reaction was used to study the effect of N-doping of activated carbon support on the catalytic activity of Pd catalysts. Activated carbon was doped using pyridine and 1,10-phenantroline, reaching nitrogen contents of 0.42-1.22 and 1.35-4.19 % (w), respectively. All catalysts (0.75 % Pd w, carbon basis) showed relatively large Pd nanoparticles (35-55nm), but they exhibited fast and complete 4-chlorophenol disappearance in batch experiments. In runs at 30°C 4-chlorophenol disappearance was mainly ascribed to hydrodechlorination, although N-doping of the support also increased adsorption. Catalysts with supports doped with pyridine yielded higher 4-chlorophenol disappearance rate in spite of lower bulk nitrogen content, however they showed higher concentration of nitrogen species at the external surface and lower loss of surface area during the doping. 4-chlorophenol disappearance rate was boosted at 60°C, with minor differences between catalysts with undoped and N-doped supports, but generation of cyclohexanone was only observed for the ones with doped support. Phenol generation simultaneous to 4-chlorophenol disappearance was observed with all the catalysts. However, subsequent hydrogenation to cyclohexanone ocurred only with the catalysts supported on N-doped activated carbon