摘要
本文采用密度泛函理论的方法计算柴油中所含部分烷烃的碳碳键间的键裂解能,与实验数据相互印证找出精度更好的方法。并通过分析理论计算结果,总结柴油中代表烃类的断键规律。采用B3LYP、B3P86、MPWB95、B1B95方法,结合6-311++G**、6-31+G**基组对标题物进行计算研究。结果表明MPWB95和B3LYP方法均可较为准确地预测出烷烃的键裂解能。由计算各种烷烃的键裂解能(BDE)可知,含有偶数碳原子数的正构烷烃的对称性比含奇数碳原子数的对称性高,而正构烷烃在断键时是在直链中间进行断裂的,因此含有偶数碳原子数的正构烷烃的键裂解能要比相邻的含有奇数碳原子数的烷烃的键裂解能要大。随着碳原子数的增加,正构烷烃的前线轨道能级差ΔE_gap大体趋势是有略微的减小。主链碳原子数相同的异构烷烃,随着侧链碳原子数的增加,其前线轨道的ΔE_gap略有减少。含碳原子总数相同的异构烷烃的ΔE_gap略小于对应正构烷烃的ΔE_gap。
Theoretical studies with density functional theory （DFT） methods were performed on the bond dissociation energies （BDEs） of a series of alkanes in diesel oil. The much more accurate methods were determined from comparing experimental values. Analyzing the theoretical results was adopted to examine the bond dissociation rule of typical alkanes in diesel oil. Computations were performed on title compounds, using B3LYP, MPWB95, B3P86 and B1B95 functionals with 6-31 I＋＋G＊＊ and 6-31＋G＊＊ basis sets. The results indicated that the B3LYP and MPWB95 functionals all could precisely measure BDEs of the alkanes. Because of the higher symmetry of the n-alkanes that contain even carbon atoms number and bond dissociating in the middle chain, the BDEs of the n-alkanes that contain even carbon atoms number are larger than those of the adjacent n-alkanes that contain odd number of carbon atoms. The frontier orbital energy gap （△Egap） of n-alkanes decreases slightly with the carbon number increasing. The △Egapof iso-alkanes containing same numerary carbon atoms in main chain decreases slightly when the branched carbon number increases. For alkanes with the same number of carbon atoms, the △Egap of isalkanes is less than that ofn-alkanes.
出处
《计算机与应用化学》
CAS
CSCD
北大核心
2012年第6期661-664,共4页
Computers and Applied Chemistry
基金
国家自然科学基金资助项目(21101070)
关键词
烷烃
热分解
键裂解能
密度泛函理论
alkane
pyrolysis
bond dissociation energy
density functional theory
