Hydrodechlorination of 4-chlorophenol in water using Rh–Al pillared clays

Abstract

Catalytic hydrodechlorination (HDC) of 4-chlorophenol (4-CP) was studied using catalysts based on Al-pillared clays containing Rh. The Rh–Al pillared clays synthesized showed highly stable and no Rh leaching was detected. Two different hydrogen sources were used for this reaction with fairly different results. When using hydrogen gas, complete 4-CP removal was achieved even at mild operating conditions (25 °C, atmospheric pressure). The use of formic acid led to substantially lower conversion (65%) for equivalent reaction time, even when the reaction temperature was increased to 90 °C. The influence of Rh load and reaction temperature on the catalytic activity of Rh–Al pillared clays was checked. The stability of the catalyst was tested in repeated consecutive runs. A progressive increase of the catalytic activity was found up to the third reaction cycle due to the successive reduction of the metallic phase of the catalyst. After that, a decrease of activity was observed, probably due to the damage of the microporous structure.