Deep insight into the catalytic removal mechanism of a multi-active center catalyst for chlorobenzene: an experiment and density functional theory study

Catalytic oxidation is considered to be the most promising dioxin purification removal technologies due to its high efficiency and low consumption, as well as no secondary pollution will be caused. In this work, a multi-active center system of catalysts was prepared by equal volume impregnation method, and their catalytic removal of chlorobenzene (CB) were investigated, which shows excellent CB conversion and CO2 selectivity. Pd0.12V4/TiO2 catalyst shows the lowest T90 (256.6 ℃) and activation energy (Ea) (8.29 kJ·mol-1). Various analytical techniques, such as XRD, TEM, XPS, H2−TPR, in situ DRIFT, Density functional theory (DFT), etc, were carried out for a deep study of CB catalytic removal mechanism. According to the results, all the components (PdOx, VOx and TiO2) of the catalyst play an indispensable role in CB oxidation removal, and the redox cycle (2V4+ (Ti3+) +Pd2+↔2V5+ (Ti4+) +Pd0) is attributed for its superior CB catalytic performance. Additionally, −C−Cl bond in CB molecule preferentially dissociates and Cl atom remains on Pd adsorption site, Bronsted acidic in TiO2 and VOx (−Ti−OH and −V−OH) provided sufficient H protons to react with Cl species (−Pd−*Cl and Clfree), and forming the HCl which facilitating Cl atom desorption. Subsequently, the C number of C6H5* gradually decreased and is oxidized to CO2 and H2O under the action of Olatt and Oads.