An experimental and modeling study on the low-temperature oxidation of methylcyclopentane in a jet-stirred reactor

Abstract

Cycloalkanes are important compounds of conventional petroleum-based fuel. Methylcyclopentane (MCP) is a representative five-membered ring cycloalkane, but studies on its oxidation behavior are still limited. Therefore, a comprehensive experimental and kinetic study on MCP low-temperature oxidation was conducted. The experiments were carried out in a jet-stirred reactor (JSR) at the equivalence ratios of 0.5, 1.0 and 2.0, in the temperature range T = 500–1100 K and at atmospheric pressure. Mole fractions of MCP, oxygen, CO, CO2 and other intermediates during fuel oxidation were measured using a gas chromatograph, at the residence time of 2 s and initial fuel mole fraction of 0.5%. Further, a detailed MCP oxidation kinetic model including both high- and low-temperature reaction pathways was developed based on the models reported in the literature, and the updated model was validated against the mole fraction profiles of the oxidation species measured in this study, and the ignition delay times in the literature. To improve the model performance, the rate constants of beta-scission reactions of methylcyclopentyl radicals were calculated at CCSD(T)/CBS//M06-2X/6–311++G(d,p) level of theory by solving the Rice-Ramsperger-Kassel-Marcus/Master Equation. The results show that our updated model has a satisfactory agreement with the oxidation species mole fraction profiles in current study and the ignition delay times in the literature. Reaction pathway analysis indicates that the reactivity difference at different equivalence ratios is attributed to the branching ratios of beta-scission reactions of methylcyclopentyl radicals.