羟基自由基对烷基化环己烷吸氢反应的多结构变分动力学研究——从理论动力学到模型意义

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-09-30 DOI:10.1016/j.combustflame.2025.114486

Yiwei Li , Mo Yang , Jingbo Wang , Xiangyuan Li

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引用次数: 0

摘要

烷基化环烷烃的自由基抽氢是燃烧和大气化学中的一个基本反应。研究了甲基环己烷（MCH）、乙基环己烷（ECH）、正丙基环己烷（nPCH）和1,3,5-三甲基环己烷（T135MCH）与羟基（ȮH）自由基在较宽温度范围（200 - 2000 K）下的反应动力学。利用M05-2X/MG3S密度泛函，利用多结构正则变分过渡态理论和小曲率隧道（MS-CVT/SCT）方法进行了高阶量子化学计算，并对CCSD(T)-F12a/jun-cc-pVDZ基准计算进行了验证。非调和效应对反应速率有显著影响，其次是重交效应，而隧道效应在燃烧相关温度下仍然较小。研究表明，单侧链环烷烃与多侧链环烷烃之间或不同侧链环烷烃之间的简单类比是不可靠的。分支比表明叔碳位在低温下起主导作用，不同的仲碳位随着温度的升高而变得更具竞争性。为了验证计算出的速率常数对激波管（ST）和快速压缩机（RCM）实验中点火延迟时间和喷射搅拌反应器（JSR）燃料浓度预测的影响，对计算出的速率常数进行了更新，并应用于相应的模型。分析结果表明，这些反应在烷基化环己烷低温氧化过程中起着至关重要的作用，从而延长了点火延迟时间，并改进了各种更新模型对燃料比浓度的预测。

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Multi-structural variational kinetics study on hydrogen abstraction reactions of Alkylated Cyclohexanes by Hydroxyl Radical — from theoretical kinetics to modeling implications

Hydrogen abstraction by radicals from alkylated cycloalkanes is a fundamental reaction in combustion and atmospheric chemistry. This study investigates the reaction kinetics of four representative cycloalkanes, methylcyclohexane (MCH), ethylcyclohexane (ECH), n-propylcyclohexane (nPCH), and 1,3,5-trimethylcyclohexane (T135MCH), with hydroxyl (ȮH) radicals over a wide temperature range (200 – 2000 K). High-level quantum chemical calculations are performed using the multi-structural canonical variational transition state theory with small-curvature tunneling (MS-CVT/SCT) method, employing the M05-2X/MG3S density functional, which is validated against CCSD(T)-F12a/jun-cc-pVDZ benchmark calculations. The anharmonicity effects exert a pronounced influence on reaction rates, followed by notable contributions from recrossing effects, while tunneling effects remain minor at combustion relevant temperatures. Fuel molecular effects on site-specific reactions are identified, which show that simple analogy is unreliable between single- and multi-side-chain cycloalkanes, or among cycloalkanes with varying side-chain lengths. The branching ratios indicate the predominant role of tertiary carbon site at low temperatures, with distinct secondary carbon site becoming more competitive as temperature increases. To demonstrate the effects of the calculated rate constants on predicting ignition delay times from shock tube (ST) and rapid compression machine (RCM) experiments and fuel concentrations from a jet-stirred reactor (JSR) using existing fuel kinetic models, the calculated rate constants are updated and applied to the corresponding models. Analysis results show that these investigated reactions are crucial during low-temperature oxidation processes of alkylated cyclohexanes, leading to longer ignition delay times and improved predictions of specific fuel concentrations with the various updated models.

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

期刊介绍： The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on: Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including: Conventional, alternative and surrogate fuels; Pollutants; Particulate and aerosol formation and abatement; Heterogeneous processes. Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including: Premixed and non-premixed flames; Ignition and extinction phenomena; Flame propagation; Flame structure; Instabilities and swirl; Flame spread; Multi-phase reactants. Advances in diagnostic and computational methods in combustion, including: Measurement and simulation of scalar and vector properties; Novel techniques; State-of-the art applications. Fundamental investigations of combustion technologies and systems, including: Internal combustion engines; Gas turbines; Small- and large-scale stationary combustion and power generation; Catalytic combustion; Combustion synthesis; Combustion under extreme conditions; New concepts.