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

摘要

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 incipient-wetness 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°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.