New Pd/hierarchical macro-mesoporous ZrO 2, TiO 2 and ZrO 2-TiO 2 catalysts for VOCs total oxidation

Abstract

Macro-mesoporous ZrO 2, TiO 2 and ZrO 2-TiO 2 have been synthesized and used as catalytic supports for volatile organic compounds (VOCs) oxidation. These supports present high surface areas. Stability of the porous structure is observed after calcination at 400 °C for ZrO 2-TiO 2 and TiO 2 but partial breakdown of the structure occurs for ZrO 2 by the crystallization into tetragonal phase. All these Pd impregnated catalysts are found to be powerful catalysts for total oxidation of toluene and chlorobenzene. Pd/TiO 2 presents the highest catalytic potential. The lowest toluene adsorption enthalpy, the low coke content observed after the catalytic test, PdO particles easily reducible should explain the interesting catalytic behaviour of Pd/TiO 2. However, production of polychlorinated compounds PhCl x (with x = 2–6) occurs at low temperature during the chlorobenzene oxidation and this amount is lower over Pd/TiO 2-ZrO 2 compared to Pd/TiO 2. But chlorobenzene is readily converted into HCl, CO 2 and H 2O at a temperature of 530 °C.