Experimental and kinetic modeling study of premixed n-butylbenzene flames

Laminar premixed n-butylbenzene/O2/Ar flames are studied at low pressure (4.0 kPa) and three equivalence ratios (ϕ = 0.75, 1.0, and 1.79) using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). A detailed n-butylbenzene mechanism is developed to describe the decomposition of n-butylbenzene in flames as well as the growth of polycyclic aromatic hydrocarbon (PAH) species. The analysis results show that n-butylbenzene is mainly consumed by H-atom abstraction reactions under the investigated conditions. As the equivalence ratio increases, the contribution of benzylic CC bond dissociation reaction increases. Unsaturated phenylalkenes and phenyldialkenes formed from the decomposition of fuel radicals are demonstrated to be the main source of formation of indene and naphthalene in n-butylbenzene flames, especially in the lean flame. As the length of the alkyl-chain increases, the combustion of the alkylbenzene produces more unsaturated phenylalkenes and phenyldialkenes, which in turn enhances the production of indene and naphthalene, as well as the total concentration of PAHs. The model was further validated on the premixed and diffusion flame data of n-butylbenzene reported in the literature.