Atmospheric oxidation of fluorinated ethers, E143a (CF{sub 3}OCH{sub 3}), E134 (CHF{sub 2}OCHF{sub 2}), and E125 (CHF{sub 2}OCF{sub 3})
Because of the ability of chlorofluorocarbons (CFCs) to deplete stratospheric ozone, many applications have begun to employ hydrofluorocarbons (HFCs) as working fluids. HFCs contain no chlorine and are thus given ozone depletion potentials of essentially zero. Attention is now focused on global warming, with the goal of reducing greenhouse gas emissions. Air conditioners, heat pumps, and refrigeration devices that use refrigerants also use energy. They contribute to global warming both by the release of the refrigerant and by the emission of carbon dioxide and other greenhouse gases in powering the devices. The atmospheric oxidation mechanisms of E143a (CF{sub 3}OCH{sub 3}), E134 (CHF{sub 2}OCHF{sub 2}), and E125 (CHF{sub 2}OCF{sub 3}) have been investigated using experimental and ab initio methodology. The oxidation of E143a produces the stable reservoir species trifluoromethyl formate, CF{sub 3}OCOH, which further oxidizes to CF{sub 2}O and CO{sub 2}. Oxidation of E134 and E125 shows the presence of only CF{sub 2}O under the condition of high O{sub 2} concentrations. Carbonyl fluoride can be formed from two competing pathways involving the halogenated alkyl radicals formed from hydrogen abstraction of E134 and E125. CO bond fission reactions and O{sub 2} addition reactions compete to produce carbonyl fluoride and a CF{sub x}H{sub 3{minus}x} radical fragment. Computational modeling of the reaction pathways provides insight into the molecular steps of the degradation process.
- Research Organization:
- Purdue Univ., West Lafayette, IN (US)
- OSTI ID:
- 20013107
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 46; Other Information: PBD: 18 Nov 1999; ISSN 1089-5639
- Country of Publication:
- United States
- Language:
- English
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