Xiaolong Liu
Institute of Process Engineering-CAS, China
Title: Catalytic oxidation of chlorobenzene over noble metals: Further insights into reaction mechanism via in-situ FTIR and DFT studies
Biography
Biography: Xiaolong Liu
Abstract
Volatile organic compounds (VOCs) emitted from the industrial plants are toxic and are dangerous to human health. Among the abundant VOCs pollutants, chlorinated volatile organic compounds (OVOCs), including chlorobenzene (CB), dichloromethane (DCM), 1, 2-dichloroethane (DCE), and trichloroethylene (TCE), are regarded as an important group of VOC pollutants due to its high toxicity, strong stability, and poor reactivity. In comparison to other noble metals (Pd, Pt, Rh), Ru catalysts have been far less explored in environmental catalysis. Recently, Ru catalysts have been well demonstrated in catalytic oxidation of alkanes, alkenes, aromatics, and some halogenated volatile organic compounds. In this work, noble metal catalysts (Pd, Pt, Ru, and Rh) were prepared and evaluated in the catalytic oxidation chlorobenzene, and Ru/TiO2 contributed the best catalytic performance. During the oxidation, polychlorinated benzenes PhClx (x≥2) were observed, and Ru/TiO2 showed apparently lower PhClx concentrations than other three samples. Besides, the dioxin-like PCBs (dl-PCBs) were collected and analyzed for Pd/TiO2 and Ru/TiO2. The ∑dl-PCBs produced by Pd/TiO2 was about 1.5 times that of Ru/TiO2. XPS analyses revealed that Ru/TiO2-used gave the lowest Cl content among the used catalysts, and the lowest (Clad+Clor)/Cl value and the highest Clbr/Cl value, which might be an important reason for its strongest chlorine removal ability and the lowest yields of polychlorinated by-products. In-situ FTIR studies were also conducted for Pd, Pt, Ru, and Rh catalysts, and various organic intermediates were observed on the catalyst surface. Besides, density functional theory (DFT) was also conducted to investigate the main reason for the difference of the catalytic performance of Ru and other three samples (Pd, Pt, and Rh). Accordingly, a reaction mechanism for the catalytic oxidation of chlorobenzene was proposed