Kinetic Modeling Analysis of the Pyrolysis of Vinyl Bromide

Abstract

A kinetic model has been developed for the thermal decomposition of vinyl bromide at temperatures below approximately 750 K. The decomposition is initiated by two channels, a pressure dependent molecular channel, C2H3Br + M → C2H2 + HBr + M, and a free radical channel, 2 C2H3Br → C2H3 + C2H3Br2. The molecular channel is second-order overall at all the temperatures and pressures investigated. The temperature dependence of the rate constant for this reaction when vinyl bromide is M is given by ln(k1a) = 35.7 ± 5.4−29.8 × 103(±12%)/T. This leads to a preexponential factor of 3 × 1015 L mol-1 s-1 and an activation energy of 248 kJ mol-1. When M is argon, the preexponential factor is 2 × 108 L mol-1 s-1 and the activation energy is 153 kJ mol-1 ± 23%. The temperature dependence of the free radical decomposition step is given by ln(k2) = 17.3 ± 3.2 − (17.3 × 103 ±13%)/T, giving a preexponential factor of 3 × 107 L mol-1 s-1 and an activation energy of 144 kJ mol-1. The model also provides kinetic data for the abstraction of hydrogen from vinyl bromide by C2H3 radicals, C2H3 + C2H3Br → C2H4 + C2H2Br. The temperature dependence of this reaction is given by ln(k3) = 28.7 ± 3.1−9.7 × 103(± 22%)/T, leading to a preexponential factor of 3 × 1012 L mol-1 s-1 and an activation energy of 81 kJ mol-1.