Theoretical study on the combustion kinetics of trimethylamine and the key intermediate N-methylmethanimine

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2024-11-22 DOI:10.1016/j.combustflame.2024.113860

Sihao Wang , Yiran Zhang , Li Fu , Hongbo Ning

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引用次数: 0

Abstract

The combustion kinetics of trimethylamine (TMA) are systematically studied based on the high-level ab initio calculations. Reaction pathways include the direct C–N and C–H bond fissions, intramolecular H-shift, and H-abstraction by five small radicals (H/CH₃/OH/NH₂/HO₂) for TMA, as well as subsequent TMA radical isomerization and decomposition. The potential energy profiles are explored at the CCSD(T)/cc-pVxZ(x = T, Q) level and the results reveal that N-methylmethanimine (MMI) is the key intermediate for TMA decomposition. Therefore, the H-abstraction reaction kinetics of MMI with H/CH₃/OH/NH₂/HO₂ radicals are also investigated. The atomization method is further adopted to determine the standard enthalpy of formation of each species, showing good agreement with the available literature results. For the H-abstraction reactions of TMA/MMI + H/CH₃/OH/NH₂/HO₂, multi-structural variational transition state theory combined with small-curvature tunneling approximation (MS-CVT/SCT) is employed to obtain the high-pressure limit (HPL) rate constants and the conventional transition state theory (TST) rate constants in MS-CVT/SCT method are obtained by CCSD(T)/cc-pVxZ(x = T, Q) energies. For the unimolecular reactions of TMA decomposition, Rice-Ramsberger-Kassel-Marcus/Master-Equation (RRKM/ME) theory is used to obtain the pressure-dependent rate constants. The calculated rate constants are also in good agreement with the available experimental results and the comparison of rate constants for four MMI formation channels shows that the β-scissions of (CH₃)₂NCH₂ to form MMI + CH₃ and CH₃NCH₃ to form MMI + H are dominant. Due to the lack of experimental data for TMA under combustion, the performance of H-abstraction reactions of MMI + H/CH₃/OH/NH₂/HO₂ is evaluated by updating a dimethylamine kinetic model and then assessed against the measured ignition delay time. It shows that the updated kinetic model can better reproduce the experimental measurements. The comprehensive kinetic details presented are invaluable for the development of kinetic model for TMA and the refinement of kinetic models for other secondary and tertiary amines.

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关于三甲胺和关键中间体 N-甲基甲亚胺燃烧动力学的理论研究

基于高水平的 ab initio 计算，对三甲胺（TMA）的燃烧动力学进行了系统研究。反应途径包括 TMA 的 C-N 和 C-H 键直接裂解、分子内 H 移位和五个小自由基（H/CH3/OH/NH2/HO2）的 H 吸取，以及随后的 TMA 自由基异构化和分解。在 CCSD(T)/cc-pVxZ(x = T, Q) 水平上对势能曲线进行了探索，结果发现 N-甲基甲亚胺 (MMI) 是 TMA 分解的关键中间体。因此，还研究了 MMI 与 H/CH3/OH/NH2/HO2 自由基的吸氢反应动力学。进一步采用原子化方法确定了各物种的标准形成焓，结果与现有文献结果吻合。对于 TMA/MMI + H/CH3/OH/NH2/HO2 的 H-萃取反应，采用了多结构变异过渡态理论结合小曲率隧道近似（MS-CVT/SCT）来获得高压极限（HPL）速率常数，而 MS-CVT/SCT 方法中的传统过渡态理论（TST）速率常数是通过 CCSD(T)/cc-pVxZ(x = T, Q) 能量获得的。对于 TMA 分解的单分子反应，则采用赖斯-拉姆伯格-卡塞尔-马库斯/主方程（RRKM/ME）理论来获得随压力变化的速率常数。计算出的速率常数与现有的实验结果也非常吻合，对四种 MMI 形成途径的速率常数进行比较后发现，(CH3)2NCH2 形成 MMI + CH3 和 CH3NCH3 形成 MMI + H 的 β 发射是主要的。由于缺乏燃烧时 TMA 的实验数据，我们通过更新二甲胺动力学模型来评估 MMI + H/CH3/OH3/NH2/HO2 的吸氢反应性能，然后根据测量的点火延迟时间进行评估。结果表明，更新后的动力学模型能够更好地再现实验测量结果。所提供的全面的动力学细节对于开发 TMA 的动力学模型以及完善其他仲胺和叔胺的动力学模型非常有价值。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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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.