Catalytic oxidation of chlorobenzene over noble metals (Pd, Pt, Ru, Rh) and the distributions of polychlorinated by-products

Xiaolong Liu; Li Chen; Tingyu Zhu; Ruliang Ning

doi:10.1016/j.jhazmat.2018.09.074

Catalytic oxidation of chlorobenzene over noble metals (Pd, Pt, Ru, Rh) and the distributions of polychlorinated by-products

J Hazard Mater. 2019 Feb 5:363:90-98. doi: 10.1016/j.jhazmat.2018.09.074. Epub 2018 Oct 3.

Authors

Xiaolong Liu¹, Li Chen², Tingyu Zhu³, Ruliang Ning⁴

Affiliations

¹ Beijing Engineering Research Center of Process Pollution Control, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China. Electronic address: liuxl@ipe.ac.cn.
² Beijing Engineering Research Center of Process Pollution Control, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China.
³ Beijing Engineering Research Center of Process Pollution Control, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address: tyzhu@ipe.ac.cn.
⁴ Beijing Engineering Research Center of Process Pollution Control, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; Chemistry and Chemical Engineering, Guizhou University, Guiyang, Guizhou 550025, China.

PMID: 30308369
DOI: 10.1016/j.jhazmat.2018.09.074

Abstract

Catalytic oxidation of chlorobenzene over noble metal catalysts Pd/TiO₂, Pt/TiO₂, Ru/TiO₂, and Rh/TiO₂ was evaluated, and Ru/TiO₂ contributed the highest catalytic activity and CO₂ selectivity. During the oxidation, polychlorinated benzenes PhCl_x (x ≥ 2) were observed, and Ru/TiO₂ showed apparently lower PhCl_x concentrations than other three samples. With the improvement of temperature, the maximum concentration appeared in the sequence of dichlorobenzene (PhCl₂), trichlorobenzene (PhCl₃), tetrachlorobenzene (PhCl₄), and pentchlorobenzene (PhCl₅), whereas the concentration of hexachlorobenzene (PhCl₆) was always low and showed no apparent regularity. Besides, the dioxin-like PCBs (dl-PCBs) were collected and analyzed for Pd/TiO₂ and Ru/TiO₂. The ∑dl-PCBs produced by Pd/TiO₂ (0.0055 ng WHO-TEQ/Nm³) was about 1.5 times that of Ru/TiO₂ (0.0027 ng WHO-TEQ/Nm³). XPS analyses revealed that Ru/TiO₂-used and Rh/TiO₂-used gave the lowest and the highest Cl content of 0.61% and 1.87%. Ru/TiO₂-used afforded the lowest (Cl_ad+Cl_or)/Cl value (22.1%) and the highest Cl_br/Cl value (77.9%), which might be an important reason for its strongest chlorine removal ability and the lowest yields of polychlorinated by-products, whereas other three catalysts showed similarity in the Cl distributions. Additionally, systematic in-situ FTIR studies were conducted, and a reaction mechanism for the catalytic oxidation of chlorobenzene was proposed.

Keywords: Catalytic oxidation; Chlorinated volatile organic compounds; Chlorobenzene; Noble metals; Polychlorinated by-products.

Publication types

Research Support, Non-U.S. Gov't