Oxidation kinetics of n-pentanol: A theoretical study of the reactivity of the 1-hydroxy-1-peroxypentyl radical
Oxidation kinetics of n-pentanol: A theoretical study of the reactivity of the 1-hydroxy-1-peroxypentyl radical
复制标题
正戊醇的氧化动力学：1-羟基-1-过氧戊基自由基反应性的理论研究
DOI：
10.1016/j.combustflame.2020.05.014
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发表时间：
2020
影响因子：
4.4
通讯作者：
Sarathy S. Mani
中科院分区：
文献类型：
--
作者：
Duan Yaozong;Monge-Palacios M.;Grajales-Gonzalez E.;Han Dong;Moller Kristian H.;Kjaergaard Henrik G.;Sarathy S. Mani
由于具有减少温室气体和污染物排放的潜力，正戊醇被认为是压燃式发动机的一种有前途的替代燃料。发动机性能很大程度上取决于燃料氧化化学，因此更准确地确定决定其氧化的反应系数对于在内燃机中使用正戊醇至关重要。人们发现涉及1-羟基-1-戊基和分子氧的反应在控制低温氧化化学中发挥着重要作用，但尚未在实验或理论上进行研究； 1-羟基-1-过氧戊基自由基的反应也是如此，该自由基是通过将氧加成到1-羟基-1-戊基的自由基中心而形成的。这项工作提出了在 CCSD(T)/aug-cc-pVTZ//M06-2X/cc-pVTZ 理论水平上进行高水平从头计算的理论研究，以揭示 1-羟基-1-过氧戊基自由基的命运。使用具有小曲率隧道校正的变分过渡态理论计算了该自由基的所有可能的分子内氢转移反应的速率系数。对于某些反应，隧道效应和变分效应非常明显，证明需要稳健的方法来解释这些效应。导致协同消除 HO2 和形成正戊醛的氢转移反应是主要途径，并控制着 1-羟基-1-过氧戊基自由基在任何温度下的反应性。因此也研究了该反应的逆反应。对于这个突出的路径，考虑了驻点的多结构（多个构象异构体）扭转非谐性的影响，以细化正向和反向速率系数。将在室温下计算的速率系数与使用先前开发的具有成本效益的多构象过渡态理论方法计算的速率系数进行比较。使用系统特定的量子 Rice-Ramsperger-Kassel (SS-QRRK) 理论来计算压力相关的速率系数，该系数表明在中温和高温下存在显着的压力依赖性。在正戊醇的化学动力学模型中应用计算的反应速率系数表明，我们计算的速率系数可以更好地了解正戊醇的化学性质，并有助于理解正戊醛是如何形成的。
n-Pentanol has been considered as a promising alternative fuel for compression-ignition engines due to its potential to reduce greenhouse gases and pollutant emissions. Engine performance is strongly dominated by fuel oxidation chemistry, and thus a more accurate determination of the coefficients of the reactions ruling its oxidation is essential for the utilization of n-pentanol in combustion engines. The reactions involving 1‑hydroxy‑1-pentyl and molecular oxygen were found to play an important role in controlling the low temperature oxidation chemistry, but have not been investigated experimentally or theoretically; this is also the case for the reactions of the 1‑hydroxy‑1-peroxypentyl radical, which is formed by the addition of oxygen to the radical center of 1‑hydroxy‑1-pentyl. This work presents a theoretical study with high level ab initio calculations at the CCSD(T)/aug-cc-pVTZ//M06-2X/cc-pVTZ level of theory to shed light on the fate of the 1‑hydroxy‑1-peroxypentyl radical. The rate coefficients of all the possible intra-molecular hydrogen shift reactions of that radical were computed using variational transition state theory with small curvature tunneling corrections. For certain reactions, tunneling and variational effects are very pronounced, proving the need for robust methodologies to account for these effects. The hydrogen shift reaction leading to a concerted HO2elimination and formation of n-pentanal is the dominant pathway and governs the reactivity of 1‑hydroxy‑1-peroxypentyl radical at any temperature. The reverse of this reaction was thereby investigated as well. For this prominent pathway, the effects of multistructural (multiple conformers) torsional anharmonicity of the stationary points were taken into account in order to refine the forward and reverse rate coefficients. The rate coefficients calculated at room temperature are compared to those calculated using a previously developed cost-effective multi-conformer transition state theory approach. The system-specific quantum Rice-Ramsperger-Kassel (SS-QRRK) theory was used to compute the pressure-dependent rate coefficients, which indicate significant pressure dependence at intermediate and high temperatures. Implementation of the calculated reaction rate coefficients in chemical kinetics models of n-pentanol revealed that our computed rate coefficients enable better insights into the chemistry of n-pentanol, and help to understand how n-pentanal is formed.