Influence of particle size and nature of Pd species on the hydrodechlorination of chloroaromatics: Studies on Pd/TiO2 catalysts in chlorobenzene conversion

TiO2 supported Pd catalysts were synthesized by two different preparation methods namely conventional impregnation (IMP) and deposition-precipitation methods (DP) using two precursor salts Pd(NO3)2 and PdCl2. The catalysts were characterized by various techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), temperature programmed reduction (TPR), CO chemisorption and BET surface area. The catalysts were evaluated for the gas phase hydrodechlorination (HDC) of chlorobenzene (CB) operating at atmospheric pressure. The catalyst prepared by deposition-precipitation using the chloride precursor (DP-Cl) exhibited higher dispersion and different electronic properties compared to the other catalysts. It also exhibited exceptional hydrodechlorination activity and stability. The generation of active electron deficient Pd species (Pdn+) on the catalyst surface appears to be the main reason for this behavior.