A highly active low Pd content catalyst synthesized by deposition-precipitation method for hydrodechlorination of chlorobenzene

Hydrodechlorination (HDC) of chlorobenzene was tested over 1 wt.% Pd supported on ZrO2 synthesized by deposition-precipitation (DP) and conventional impregnation (IMP) methods. The effect of precursor was also investigated using chloride and nitrate salts of Pd. The catalysts were characterized by CO chemisorption, BET surface area, XPS, and temperature-programmed reduction (TPR). The catalyst prepared by the DP method using chloride precursor has shown the highest activity and stability compared to the other catalysts. The variation in chlorobenzene, conversion of different catalysts is explained based on the nature of Pd species formed on the surface. A comparison of the HDC functionality of the most stable 1 wt.% catalyst with that of a 10 wt.% catalyst, prepared by the conventional impregnation method, has been made. In contrast to the general observation that the low dispersed catalysts are preferred for hydrodechlorination, it is noted that the high-dispersed catalysts prepared by the DP method offer better performance. This is a significant observation in terms of considerable reduction in palladium content and the availability of more active surface area. (C) 2004 Elsevier B.V. All rights reserved.