Experimental and kinetic modeling investigation on 2,5-hexanedione oxidation in a jet-stirred reactor

Abstract Unique resonance stabilization features of R and QOOH radicals of 2,5-hexanedione [CH3C(=O)CH2CH2C(=O)CH3] facilitated the investigation on the roles of carbonyl group in the oxidation of ketones. This work presents the first study on the speciation from the oxidation of 2,5-hexanedione. A fuel-lean (ϕ=0.5) 2,5-hexanedione/O2/Ar mixture was investigated in a jet-stirred reactor (JSR) operated at atmospheric pressure, over a temperature range of 600–900 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to acquire detailed speciation information. A detailed kinetic mechanism was proposed based on the “reaction classes” strategy and validated against the current measurements. No obvious low-temperature reactivity was observed under the investigated conditions, and the reason was attributed to the unfavored ROO = QOOH isomerization reactions of both two RO2 radicals, while the energetically favored HO2-elimination reactions produce inert HO2 radicals in the low-temperature regime. β-scission reactions dominate the consumption of fuel radicals. The prediction of fuel reactivity strongly depends on the reactions involving the small hydrocarbon species and H-atom abstraction reactions. The competition between the reaction pair of CH3+HO2 = CH3O+OH and CH3+HO2 = CH4+O2 is the most influential factor for the fuel reactivity in the studied temperature regimes. Based on the experimental observations and kinetic modeling analyses, fuel consumption and major intermediates formation pathways in 2,5-hexanedione were illustrated.