Degradation of 4-Chlorobiphenyl as a Model Compound of Polychlorinated Biphenyls with Potassium Carbonate in Supercritical Water in the Presence or Absence of Copper(II) Oxide

Abstract

In order to investigate the degradation of polychlorinated biphenyl degradation of its model compound 4-chlorobiphenyl (4-CB) with potassium carbonate in supercritical water in the presence or absence of copper(II) oxide was investigated. The reactions were carried out using two sorts of autoclaves made of sus 316 or Hastelloy X. The autoclaves were pressurized at 4–1 MPa at room temperature and heated to 500–570 °C to give the pressure of the mixture at 35–38 MPa. It was revealed that 4-CB was completely decomposed and that most of chlorine atoms were converted to potassium chloride. A gas mixture of benzene, toluene, and methane was obtained at the total yield of 10% and 4-biphenylol was obtained in the yield of 5–33% depending on the reaction conditions. Carbon skeleton of 4-CB was converted to CO₂ or HCO₃⁻ in the yield of 6–24% depending on the reaction conditions. Effect of addition of copper(II) oxide on the reaction was investigated to show that addition of copper(II) oxide brought about the increase of the yields of hydrocarbons, especially the yield of benzene at 500 °C. In addition to above stated products, water soluble and easily decomposable compounds were formed by the reactions in the present study.