Photo-decomposition of Fluorocarbons in the Air

Abstract

Air containing one of fluorocarbons (1000 ppm) such as chlorodifluoromethane (CHClF₂), chlorotrifluoromethane (CClF₃), dichlorodifluoromethane (CCl₂F₂), 1, 1-difluoroethane (C₂H₄F₂), bromochlorodifluoromethane (CBrClF₂), bromotrifluoromethane (CBrF₃), 2, 2-difluoro ethylene (C₂H₂F₂), chlorotrifluoroethylene (C₂ClF₃) and tetrafluoroethylene (C₂F₄) was irradiated by mercury lamp at room temperature. In the both cases of CCl₂F₂ and C₂ClF₃, the photo- decomposition in the presence of oxygen was faster than that in the absence of oxygen. Both carbon monoxide and carbon dioxide were observed in the irradiated gas. The initial degree of decomposition of fluorocarbons, chlorofluorocarbons, unsaturated fluorocarbons and unsaturated chlorofluorocarbons increased with the decrease in wavelength, and that of bromofluorocarEons with the increase in wavelength. The initial degree of decomposition of C₂ClF₃ with UV irradiation by a high pressure mercury lamp (100 W) was about 1000 times that of CCl₂F₂ and about 50 times that of CBrClF₂. The photo-oxidative decomposition of C₂ClF₃ also took place by sun light irradiation, 60% of C₂ClF₃ disappeared under outdoor exposure within 3 days. While in the case of CCl₂F₂, t he reaction did not occur under outdo-or exposure during one week. The reaction of C₂ClF₂w as accelerated by both chlorine and ozone, while those o f CCl₂F₂ and CBrClF₂ were not. On the other hand, CF₄ and C₂H₄F₂ scarcely affected th e decomposition of ozone, while CBrClF₂a nd C₂ClF₃ remarkably accelerated that. In the case of CCl₂F₂, t he initial degree of decomposition of ozone increased proportionally with the increase in the initial concentration of CCl₂F₂(log[CCl₂F₂]).