Abstract
In this paper, chemical reaction kinetics at low temperatures on three different methyl crotonate (MC, C5H8O2) radicals with O-2 were conducted via quantum chemical methods. The potential energy surfaces (PESs) for these reactions were investigated by M062x/6-311++G(d,p) and CBS-QB3 methods. The related rate coefficients also have been solved by master equations based on Rice-Ramsperger-Kassel-Marcus theory, predicting the competitive relationships over 300 to 1500 K and 0.001 to 100 atm. The calculated results indicated that the rate constants of O-2 addition reaction at ester methylic site were higher than those at allylic sites, which showed that the conjugation effect caused by the C=C double bond has a crucial effect on the reaction process. Formation of initial adducts and intramolecular H-transfer reactions play a great role in the low temperature oxidation of MC. Furthermore, the mechanism of O-2 addition to MC radicals was verified by the previous combustion model. The updated model did a good job to replicate the previous experimental results. This work not only provides the necessary rate constants for the reaction mechanism of MC combustion but also serves as a solid starting point for the further understanding of combustion kinetics of large molecule unsaturated biodiesels. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.