Experimental and kinetic modeling study on sooting tendencies of alkylbenzene isomers

Alkylbenzenes are major aromatic constituents of real transportation fuels and important surrogate components. In this study, 4 kinds of C8H10 and 8 kinds of C9H12 alkylbenzenes were tested in a laminar diffusion flame to investigate the influence of chemical structure on sooting tendency. The laser induced incandescence (LII) technique was applied to obtain the 2D distribution of soot volume fraction for calculating the yield sooting index (YSI) of test fuels. The processes of fuel oxidation and soot formation were simulated by a detailed chemical kinetic mechanism. The mechanism includes all C8H10 and C9H12 alkylbenzenes and includes species ranging from reactant to carbon particle. The simulation results of defined YSI were in good agreement with the experimental values. A database of sooting tendencies was established by experimental data, which shows that the number of substituents is positively correlated with the sooting tendency and that the sooting tendency of meta-substituent species is higher than other isomers. Through the analysis of reaction pathway and sensitivity, it was found that the main production pathway of A4 (pyrene) is via alkylbenzenes combination reactions at the early stage of combustion. The experimental database presented in this study is systematic and comprehensive for C8H10 and C9H12 alkylbenzenes, and is thus expected to be useful for soot model development and validation.

Automated summary

This study investigated the influence of chemical structure on sooting tendency of alkylbenzenes in transportation fuels. Experimental data showed a positive correlation between the number of substituents and sooting tendency, with meta-substituent species exhibiting higher sooting tendency. Simulation results agreed well with experimental values, contributing to the establishment of a systematic and comprehensive database for further soot model development and validation.