Kinetic modeling of the benzyl + HO2 reaction
Kinetic modeling of the benzyl + HO2 reaction
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DOI：
10.1016/j.proci.2008.05.040
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发表时间：
2009-01-01
影响因子：
3.4
通讯作者：
Bozzelli, Joseph W.
中科院分区：
文献类型：
--
作者：
da Silva, Gabriel;Bozzelli, Joseph W.
苄基是一种共振稳定的自由基，通常作为芳香族化合物燃烧的中间体出现。苯与HO2的双分子反应在甲苯氧化过程中起重要作用，特别是在中低温条件下，苯自由基的单分子分解速度较慢。我们发现，在苯基的亚甲基位点上加成HO2会产生振动激发的苯基过氧化氢加合物，在基态以上产生超过60 kcal mol(-1) （251 kJ mol(-1)）的多余能量。利用从头计算得到的热化学和动力学参数，采用变分过渡态理论（VTST）处理无障自由基+自由基反应动力学，对苯+ HO2反应进行了RRKM模拟。结果表明，在800 K及以上温度下，苯+ HO2反应主要生成苯氧基+ OH，在较低温度下主要生成稳定的过氧化氢苯分子。在理论的G3B3水平上，苯自由基的生成热计算为52.5 kcal mol(-1) (219.7 kJ mol(-1))，与最近对该值的其他测定相对一致。(C) 2009燃烧研究所。Elsevier Inc.出版。版权所有。
Benzyl is a resonantly stabilized radical that commonly occurs as an intermediate in the combustion of aromatic compounds. The bimolecular reaction of benzyl with HO2 is important in the oxidation of toluene, especially at low to moderate temperatures, where unimolecular decomposition of the benzyl radical is slow. We show that the addition of HO2 to the methylene site in benzyl produces a vibrationally excited benzylhydroperoxide adduct, with over 60 kcal mol(-1) (251 kJ mol(-1)) of excess energy above the ground state. RRKM simulations are performed on the benzyl + HO2 reaction, using thermochemical and kinetic parameters obtained from ab initio calculations, with variational transition state theory (VTST) for treatment of barrierless radical + radical reaction kinetics. Our results reveal that the benzyl + HO2 reaction proceeds predominantly to the benzoxyl radical + OH at temperatures of around 800 K and above, with the production of stabilized benzylhydroperoxide molecules dominating at lower temperatures. The heat of formation of the benzyl radical is calculated as 52.5 kcal mol(-1) (219.7 kJ mol(-1)) at the G3B3 level of theory, in relative agreement with other recent determinations of this value. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.