Experimental and kinetic model studies of 2,3-dimethylhexane pyrolysis at atmospheric pressure

Isomers of alkanes have a significant effect on their combustion performance. In order to better understand the effect of the number of methyl side chains on fuel performance, the pyrolysis experiments of 2,3-dimethylhexane (C₈H₁₈–23) were carried out by using a jet-stirred reactor and the synchrotron vacuum ultraviolet photoionization mass spectrometry at 770 - 1130 K and at atmospheric pressure. Key pyrolysis products, such as acetylene, ethylene, propene, 1,3-butadiene, 2-butene, 1-pentene, 2-methyl-2-butene, 2-methyl-2-hexene, 3-methyl-2-hexene, as well as benzene, styrene and naphthalene, etc., were identified and measured. A detailed kinetic model of C₈H₁₈–23 pyrolysis, including 1756 species and 6023 reactions, was constructed and validated against the experimental results in the present work. Rate of production and sensitivity analysis of C₈H₁₈–23 showed that the major consumption pathways are H-abstractions and unimolecular dissociation reactions, with the highest contributions from those at/between C(2) and C(3) atoms. Theoretical comparison of the pyrolysis of the three isomers of C₈H₁₈ hydrocarbon, i.e., C₈H₁₈–23, 2-methylheptane and n-octane, shows that with increasing of the number of methyl side chains, C₈H₁₈ will be more reactive in pyrolysis and be more effective in producing soot precursors.