Kinetic modeling of benzene decomposition near 1000 K: The effects of toluene impurity

Kinetic data of Brooks et al. [3] on the decomposition of C6H6 near 1000 K have been analyzed by computer modeling. The observed overall 3/2-order kinetics could be accounted for by a mechanism composed of 4 key reactions involving H atoms and C6H5 radicals using recently acquired rate constants. However, the appearance of CH4 and the enhanced H2 yields could only be explained by invoking the reactions of ∼0.1% of toluene present in the system as reported by the authors. Overall, the decomposition reaction is dominated by the unimolecular dissociation of C6H6 followed by the short chain process, H + C6H6 = C6H5 + H2 and C6H5 + C6H6 = C12H10 + H, which result in the dehydrogenation of C6H6, producing C12H10 + H2. In order to account for the yield of H2 quantitatively, the displacement reaction, C6H5CH2 + C6H6 = CH2(C6H5)2 + H, was invoked and modeled to have the approximate rate constant, 8.4 × 1011 exp(−11800/T) cm3 mol−1 s−1.