碳氢化合物燃烧中间体Lennard-Jones系数的计算

在已有的基团贡献法公式的基础上,提出了一种新的基团贡献法公式,并通过拟合250种化合物(包括185种稳定化合物临界性质的实验值和65种自由基临界性质的计算值)的临界性质得到了40种基团的贡献值,并用于预测未知化合物的临界性质.选取了训练集以外的、有临界性质实验值的30种化合物作为独立测试集,用于验证所建模型对临界性质的预测能力,T_C和P_C平均绝对偏差分别为8.52%和16.83%.结果表明,预测结果和实验值相吻合,该模型可以用于大分子化合物及自由基的临界性质预测.根据临界性质与Lennard-Jones(L-J)系数的经验关系式,预测了碳氢化合物燃烧中间体的L-J系数,得到独立测试集46种碳氢化合物的L-J系数,与文献值接近,T_C和P_C的平均绝对偏差分别为9.88%和9.96%.比较了训练集中烷烃自由基·C_6H_(13)、烯烃自由基·C_5H_9和炔烃自由基·C_5H_7同分异构体的L-J系数,同时,将己烷自由基·C_6H_(13)与相似的邻近烷烃C_6H_(14)的L-J系数进行比较,发现同分异构体之间或相似化合物之间L-J系数有较大偏差.此外,对缺少L-J系数的114种常见碳氢化合物自由基进行了预测.这对于碳氢化合物的燃烧模拟及基元反应中压强相关的速率常数计算有重要意义.

Studies on the Calculation of Lennard-Jones Parameters for Intermediates in Hydrocarbon Combustion?

Lennard-Jones(L-J) parameters were used in combustion modeling as transport parameters and in pressure-dependent rate-coefficient calculations as collision rate parameters. However, there are no reported values for most of the radical intermediates in hydrocarbon combustion. In this work, a new group contribution formula was proposed and group contribution values of 40 groups for intermediates in the combustion of hydrocarbons were fitted from critical properties of 250 species, including 185 stable species with experimental critical property values and 65 radical species with calculated critical property values and these group contribu-tion values were used to estimate critical properties for new species. 30 hydrocarbon compounds with available experimental properties were chosen to validate the accuracy of the model, the average absolute deviation of TC and PC were 8. 52% and 16. 83% , respectively, showing an agreement with experimental data. This model can predict critical properties for macromolecular and radical species. According to the empirical relations between critical properties and L-J parameters, L-J parameters of hydrocarbon combustion intermediates were estimated. It was shown that the predicted values for 46 compounds with available reported data were in good agreement with the reported values and the average absolute deviation of TC and PC were 9. 88% and 9. 96% , respectively. The L-J parameters of alkane radical · C6 H13 , alkene radical · C5 H9 and alkyne radical · C5 H7 isomers were compared. L-J parameters of · C6 H13 and similar compound C6 H14 were also compared and the results showed that there were obvious differences of the L-J parameters between isomers or between similar compounds. In addition, L-J parameters for 114 hydrocarbon radicals, for which L-J parameters had not been reported yet, were predicted. These data are important in the combustion modeling of hydrocarbons and pressure-dependent rate-coefficient calculations for elementary reactions in hydrocarbon combustion.