Gas-phase reaction of halon 1211 (CBrCIF2) with methane

The nonoxidative gas-phase reaction of halon 1211 (CBrClF2) with methane wa s studied using a tubular plug-flow alumina reactor at atmospheric pressure , over the temperature range of 673-1073 K, and at residence times between 0.1 and 1.3 s. With an equimolar feed of CBrClF2 and CH4, complete halon co nversion was achieved at 1073 K for all residence times considered. The ini tial products of the reaction are CHClF2 and CH3Br, which are replaced by C 2H2F2 at elevated temperatures. We suggest C2H2F2 is produced from the dire ct coupling of CH3 and CF2Cl radicals, which rapidly decompose to C2H2F2 an d HCl. Minor products formed during reaction include C2H3F, CHF3, C2F4, CHB rF2, and C2HBrF2. The formation of CHClF2, C2F4, CHBrF2, and C2HClF2 was ob served to reach a maximium at specific residence times, and formation of so ot was detected above 943 K. Possible mechanistic pathways for major and so me minor species are discussed.