Hydrodechlorination of 2,3,5-Trichlorophenol in Methanol/Water on Carbon Supported Pd-Rh Catalysts

Abstract

Catalytic hydrodechlorination of 2,3,5-trichlorophenol was studied over 0.97%Pd/C, 0.98%Rh/C, and 0.8%Pd/0.19%Rh/C catalysts in various methanol/water mixtures. The catalysts were prepared by incipientwetness impregnation of carbon support and characterized by Brunauer-Emmet-Teller (BET) surface area, temperature-programmed reduction (TPR), and X-ray diffraction (XRD) methods. Increasing calcination temperature caused an increase in crystallite size, whereas the initial hydrodechlorination reaction rate was decreased. The catalyst calcined at the calcination temperature (400 degrees C) exhibited the highest catalytic performance; 0.97%Pd/C catalyst, which had the highest crystallite size, was found to be the most active and selective toward the formation of 2,3-dichlorophenol among other catalysts. The hydrodechlorination of 2,3,5-trichlorophenol was accelerated by increasing the percentage of methanol in water/methanol mixtures up to 50% (v/v), and beyond, where the reaction rate was slowed down. Hydrodechlorination activity of carbon-supported catalysts were in the order of Pd/C > Pd/Rh/C > Rh/C.