Experimental and computational studies on the gas-phase reaction of CBrF{sub 3} with hydrogen
Gas-phase hydrogen dehalogenation of halon 1301 (bromotrifluoromethane, CBrF{sub 3}) 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 CBrF{sub 3} and H{sub 2} increase with temperature and residence time. CBrF{sub 3} conversion increases with decreasing input volume ratio of CBrF{sub 3} to H{sub 2}. The species produced are a complex mixture of halogenated hydrocarbons including CHF{sub 3}, CH{sub 2}F{sub 2}, C{sub 2}HF{sub 3}, C{sub 2}F{sub 6}, C{sub 2}H{sub 2}F{sub 4}, C{sub 2}HF{sub 5}, CHBrF{sub 2}, CH{sub 3}Br, CH{sub 2}Br{sub 2}, CHBr{sub 2}F, and CH{sub 2}BrF in addition to HBr and HF. The production yield of CHF{sub 3}, the major product, increases with temperature to 1,023 K, after which CHF{sub 3} levels decrease with increasing temperature. Conversely, CHF{sub 3} selectivity decreases with increasing temperature, residence time, or input ratio of CBrF{sub 3} to H{sub 2}. The initiation reaction is believed to be the rupture of the C-Br bond in CBrF{sub 3}, and the radical species CF{sub 3} then reacts with H{sub 2} to produce H and CHF{sub 3}. The key step in the process is the attack of H radical on CBrF{sub 3} to produce CF{sub 3} and HBr. Experimental data are compared with the model predictions, and good agreement between experimental and modeling prediction is obtained for CHF{sub 3} production. However, the existing mechanism does not predict the formation of CHBrF{sub 2}, which is detected during the experimental study, and the concentrations of CH{sub 2}F{sub 2} and C{sub 2}F{sub 6} 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.
- Research Organization:
- Univ. of Newcastle, Callaghan, New South Wales (AU)
- OSTI ID:
- 20020730
- Journal Information:
- Environmental Science and Technology, Vol. 34, Issue 4; Other Information: PBD: 15 Feb 2000; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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