Liu Mingxia, Hui Xin, Xue Xin, Lin Yuzhen, Zhou Chong-Wen
School of Energy and Power Engineering, Beihang University, Beijing 100191, P. R. China.
National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing, 100191, P. R. China.
Phys Chem Chem Phys. 2023 Apr 12;25(15):10795-10810. doi: 10.1039/d2cp03726b.
Chemical kinetic studies of hydrogen atom abstraction reactions by hydroperoxyl (HȮ) radical from six alkyl cyclohexanes of methyl cyclohexane (MCH), ethyl cyclohexane (ECH), -propyl cyclohexane (PCH), iso-propyl cyclohexane (iPCH), -butyl cyclohexane (BCH), and iso-butyl cyclohexane (iBCH) are carried out systematically through high-level calculations. Geometry optimizations and frequency calculations for all species involved in the reactions are performed at the M06-2X/6-311++G(d,p) level of theory. Electronic single-point energy calculations are calculated at the UCCSD(T)-F12a/cc-pVDZ-F12 level of theory, with zero-point energy corrections. High-pressure limit rate constants for the reactions of alkyl cyclohexanes + HȮ, in the temperature range of 500-2000 K, are calculated using conventional transition state theory taking asymmetric Eckart tunneling corrections and the one-dimensional hindered rotor approximation into consideration. Elementary reaction rate constants and branching ratios for each alkyl cyclohexane species were investigated, and rate constant rules of primary, secondary, and tertiary sites on the side-chain and the ring are provided here. Additionally, temperature-dependent thermochemical properties for reactants and products were also obtained in this work. The updated kinetics and thermochemistry data are used in the alkyl cyclohexane mechanisms to investigate their effects on ignition delay time predictions of shock tube and rapid compression machine data, and species concentrations from a jet-stirred reactor. It is found that these investigated reactions promote ignition delay times in the temperature range of 800-1200 K and also improve the prediction of cyclic olefin species formation which stems from the decomposition of fuel radicals.
通过高水平计算系统地开展了氢过氧自由基（HȮ）从甲基环己烷（MCH）、乙基环己烷（ECH）、正丙基环己烷（PCH）、异丙基环己烷（iPCH）、正丁基环己烷（BCH）和异丁基环己烷（iBCH）这六种烷基环己烷中夺取氢原子反应的化学动力学研究。反应中涉及的所有物种的几何结构优化和频率计算均在M06 - 2X/6 - 311++G(d,p)理论水平下进行。电子单点能量计算在UCCSD(T)-F12a/cc-pVDZ-F12理论水平下进行，并进行零点能量校正。在500 - 2000 K的温度范围内，使用传统过渡态理论并考虑不对称埃卡特隧道效应校正和一维受阻转子近似，计算了烷基环己烷 + HȮ反应的高压极限速率常数。研究了每种烷基环己烷物种的基元反应速率常数和分支比，并给出了侧链和环上伯、仲、叔位点的速率常数规律。此外，本工作还获得了反应物和产物随温度变化的热化学性质。更新后的动力学和热化学数据被用于烷基环己烷反应机理中，以研究它们对激波管和快速压缩机数据的点火延迟时间预测以及喷射搅拌反应器中物种浓度的影响。研究发现，这些反应在800 - 1200 K的温度范围内促进了点火延迟时间，并且还改善了源于燃料自由基分解的环状烯烃物种形成的预测。
