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首页> 外文会议>International Symposium on Combustion; 20060805-11; University of Heidelberg(DE) >On the formation and decomposition of C_7H_8
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On the formation and decomposition of C_7H_8

机译：关于C_7H_8的形成与分解

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The kinetics of reactions on the C_7H_8 surface were studied with state-of-the-art ab initio transition state theory (TST) and master equation methodologies. A priori predictions of the capture rate for C_6H_5 + CH_3 and for C_7H_7 + H are obtained from direct variable reaction coordinate TST simulations. These simulations employ small basis set CASPT2 interaction energies coupled with one-dimensional reaction path corrections based on higher level simulations for related reactions. For the C_7H_7 + H reaction, predictions are obtained for both the total rate and for the branching between toluene, o-isotoluene and ρ-isotoluene. A mapping of the low energy pathways for isomerization from these three C_7H_8 isomers identifies a number of processes with barriers at or below the dissociation threshold. Nevertheless, at combustion temperatures the dissociation rates are predicted to exceed the isomerization rates, and it is reasonable to treat the kinetics of each isomer as a simple single well association/dissociation equilibrium. Master equation simulations yield predictions for the temperature and pressure dependence of each of the recombination and dissociation processes, as well as for the C_7H_7 + H → C_6H_5 + CH_3 bimolecular reaction. These simulations implement collisional energy transfer probabilities based on the work of Luther and co-workers. The theoretical predictions are found to be in satisfactory agreement with the available experimental data for the photodissociation of toluene, the temperature and pressure dependent dissociation of toluene, and the reaction of benzyl radical with H. For the C_6H_5 + CH_3 recombination, the theoretical predictions exceed the experimental measurements of Lin and coworkers by a factor of 2 or more for all temperatures.
机译：使用最新的从头算过渡态理论（TST）和主方程方法研究了C_7H_8表面上的反应动力学。从直接变量反应坐标TST模拟获得C_6H_5 + CH_3和C_7H_7 + H捕获率的先验预测。这些模拟采用小基集CASPT2相互作用能，并基于相关反应的高级模拟对一维反应路径进行校正。对于C_7H_7 + H反应，可以预测总速率以及甲苯，邻异甲苯和ρ-异甲苯之间的支链。从这三个C_7H_8异构体异构化的低能途径的映射确定了许多在或低于解离阈值时具有势垒的过程。然而，在燃烧温度下，离解速率预计将超过异构化速率，并且将每种异构体的动力学视为简单的单井缔合/离解平衡是合理的。主方程模拟对每个重组和解离过程的温度和压力依赖性以及C_7H_7 + H→C_6H_5 + CH_3双分子反应产生预测。这些模拟基于路德及其同事的工作来实现碰撞能量转移的概率。理论预测与甲苯的光解离，与温度和压力有关的甲苯解离以及苄基与H的反应有关的现有实验数据令人满意。对于C_6H_5 + CH_3的重组，理论预测超过了在所有温度下，Lin和同事的实验测量结果的系数都是2或更大。

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