A Theoretical and Computational Analysis of the Methyl-Vinyl + O2 Reaction and Its Effects on Propene Combustion

A detailed analysis of the reaction of CH3CCH2 and CH3CHCH with molecular oxygen is presented. The C3H5O2 potential energy surface was characterized using a combination of electronic structure methods. The majority of the stationary points on the PES was determined at the CCSD­(T)-F12a/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ level of theory, with the remaining transition states computed using multireference methods. Microcanonical rate theory and the master equation are used to determine the temperature- and pressure-dependent rate coefficients for each reaction channel. The main product channels are CH2O + CH3CO for CH3CCH2 and CH3CHO + CHO for CH3CHCH. The rate constants for these two reactions at 1 atm are k = 9.03 × 1022 × T–3.21 × exp–2162/T and 1.50 × 1019 × T–2.10 × exp–1260/T cm–3 mol–1 s–1, respectively. In contrast to C2H3 + O2, the methyl-vinyl + O2 reactions remain chain propagating, even at high temperatures. The new rate coefficients were implemented in a detailed mechanism taken from the literature. These changes have a modest effect on the ignition delay time and laminar flame speeds for propene combustion.本文针对CH3CCH2与CH3CHCH与分子氧的反应开展了详尽分析。本研究采用多种电子结构方法联用的方式，对C3H5O2势能面（Potential Energy Surface，简称PES）进行了表征。该势能面上的绝大多数驻点均通过CCSD(T)-F12a/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ理论级别计算得到，剩余过渡态则采用多参考态方法完成计算。本研究借助微正则速率理论与主方程，求解得到各反应通道的温度与压力依赖型速率系数。对于CH3CCH2体系，主要产物通道为CH2O与CH3CO；对于CH3CHCH体系，主要产物通道则为CH3CHO与CHO。上述两个反应在1标准大气压下的速率常数分别为：k = 9.03 × 10²² × T⁻³·²¹ × exp(−2162/T) 与 1.50 × 10¹⁹ × T⁻²·¹⁰ × exp(−1260/T) cm³·mol⁻¹·s⁻¹。相较于C2H3与O2的反应，即便在高温环境下，甲基乙烯基与分子氧的反应仍保持链传播特性。本研究将全新得到的速率系数整合至取自文献的详细反应机理中。上述调整对丙烯燃烧的点火延迟时间与层流火焰速度仅产生小幅影响。