Rate constants for the H abstraction from alkanes (R-H) by R′O•2 radicals: A systematic study on the impact of R and R′
Rate constants for the H abstraction from alkanes (R-H) by R′O•2 radicals: A systematic study on the impact of R and R′
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DOI：
10.1016/j.proci.2006.08.091
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发表时间：
2007-01-01
影响因子：
3.4
通讯作者：
Deutschmann, Olaf
中科院分区：
文献类型：
--
作者：
Carstensen, Hans-Heinrich;Dean, Anthony M.;Deutschmann, Olaf
低温燃烧中柴恩分支的一个可能来源是烷基过氧化氢(R‘OOH)的热分解。这些物种的一种产生方式是通过烷基过氧基R‘O-2(中心点)从烷烃(RH)上进行H原子抽提反应。早期关于HO2中心点、CH3O2中心点和C2H5O2中心点从乙烷中提取乙烷的研究表明，这些反应对乙烷/02混合物的计算着火时间有显著影响。另一个结果是，CH3O2中心点和C2H5O2中心点的抽提速率常数基本相同，但小于HO2中心点。关联的活化能遵循Evans-Polanyi关系，而一个公共的A因子可以在大约2-3的因子内描述所有三个反应的动力学。在这项研究中，我们通过(1)考虑一组烷烃(RH=CH4，C2H6，C3H8，C4H10)和(2)包括额外的过氧基物种(R‘O’(2)，其中R‘=H，CH3，C2H5，C3H7，C4H9，HC=O和CH3C=O)来扩展研究。我们给出了总共32个反应的速率常数，并分析了关于反应性的系统趋势的数据。结果表明，反应速率常数按酰基过氧基>；HO2中心点>；烷基过氧基的顺序递减。不同C-H键的反应性随键强度的变化而变化。总体而言，反应热是主要的控制参数，但不是唯一的速率常数。讨论了计算的准确性和结果的含义。(C)2006年，燃烧研究所。爱思唯尔公司出版，版权所有。
A possible source of chai n-branching in low temperature combustion is thermal decomposition of alkyl hydroperoxides (R'OOH). One way these species can be produced is via H atom abstraction reactions from alkanes (RH) by alkylperoxy radicals R'O-2(center dot). An earlier study focussing on the abstraction from ethane by HO2 center dot, CH3O2 center dot; and C2H5O2 center dot, revealed that these reactions have a noticeable impact on calculated ignition times of ethane/02 mixtures. Another outcome was that the abstraction rate constants for CH3O2 center dot and C2H5O2 center dot are virtually identical but smaller than that for HO2 center dot. The associated activation energies followed an Evans-Polanyi relationship while a common A-factor could be used to describe the kinetics of all three reactions within a factor of about 2-3. In this current study, we extend the investigation by (1) considering a set of alkanes (RH = CH4, C2H6, C3H8, C4H10) and (2) by including additional peroxy species (R'O'(2) with R'= H, CH3, C2H5, C3H7, C4H9, HC=O, and CH3C=O). We present rate constants for a total of 32 reactions and analyze the data with respect to systematic trends in the reactivity. The results reveal that the rate constants decrease in the order acylperoxy > HO2 center dot > alkylperoxy. The reactivity of different C-H bonds follows the bond strengths. Overall the heat of reaction is found to be the dominant but not the only rate constant controlling parameter. The accuracy of the calculations and implications of the results are discussed. (C) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.