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Experimental and computational studies on the gas-phase reaction of CBrF3 with hydrogen

Li, K., Kennedy, E.M., Moghtaderi, B. and Dlugogorski, B.Z. (2000) Experimental and computational studies on the gas-phase reaction of CBrF3 with hydrogen. Environmental Science & Technology, 34 (4). pp. 584-590.

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Gas-phase hydrogen dehalogenation of halon 1301 (bromotrifluoromethane, CBrF3) has been studied experimentally in a tubular alumina reactor operating at atmospheric pressure. It is found that hydrogen can accelerate the decomposition of halon 1301 and that conversion levels of CBrF3 and H2 increase with temperature and residence time. CBrF3 conversion increases with decreasing input volume ratio of CBrF3 to H2. The species produced are a complex mixture of halogenated hydrocarbons including CHF3, CH2F2, C2HF3, C2F6, C2H2F4, C2HF5, CHBrF2, CH3Br, CH2Br2, CHBr2F, and CH2BrF in addition to HBr and HF. The production yield of CHF3, the major product, increases with temperature to 1023 K, after which CHF3 levels decrease with increasing temperature. Conversely, CHF3 selectivity decreases with increasing temperature, residence time, or input ratio of CBrF3 to H2. The initiation reaction is believed to be the rupture of the C-Br bond in CBrF3, and the radical species CF3 then reacts with H2 to produce H and CHF3. The key step in the process is the attack of H radical on CBrF3 to produce CF3 and HBr. Experimental data are compared with the model predictions, and good agreement between experimental and modeling prediction is obtained for CHF3 production. However, the existing mechanism does not predict the formation of CHBrF2, which is detected during the experimental study, and the concentrations of CH2F2 and C2F6 measured experimentally are significantly different from those predicted. Modifications to the existing NIST mechanism are suggested to improve the prediction of the quantity of these species produced.

Publication Type: Journal Article
Publisher: American Chemical Society
Copyright: © 2000 American Chemical Society
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