Pyrolysis Kinetics for Long-Chain n-Alkylbenzenes: Experimental and Mechanistic Modeling Results

We developed a reaction model for the pyrolysis of long-chain n-alkylbenzenes in order to determine the influence of the alkyl chain length on the pyrolysis kinetics. The model, which has as its basis the previously deduced free-radical reaction mechanism for alkylbenzene pyrolysis, incorporates the effect of the alkyl chain length on the reaction path degeneracy for the hydrogen-abstraction steps. The kinetics predicted by the reaction model for pyrolyses at 400 °C and an initial reactant concentration of 1.3 M were in good accord with experimentally determined pseudo-first-order rate constants for seven different n-alkylbenzenes having aliphatic substituents ranging from butyl (C₄) to pentadecyl (C₁₅).