正己烷+1-丁基-3-甲基咪唑硫氰酸盐的分子动力学

Molecular dynamics of n-hexane+1-butyl-3-methylimidazolium thiocyanate binary system

离子液体由于优异的分离性能被用于各种烷烃和烯烃的萃取精馏过程。为了从理论层面揭示离子液体作为萃取剂的微观机理,采用分子动力学方法对正己烷和1-丁基-3-甲基咪唑硫氰酸盐([BMIM][SCN])二元混合溶液进行NPT和NVT动力学模拟,计算体系的密度和黏度;使用4种径向分布函数(正己烷-正己烷、正己烷-阳离子、正己烷-阴离子、阳离子-阴离子)剖析体系的微观结构,利用平均约化密度梯度法(aRDG)分析体系中的弱相互作用的来源和稳定性。模拟结果表明:正己烷和[BMIM][SCN]混合物系互溶性差,但随着离子液体浓度的增加,两者的互溶度逐渐增加;混合溶液中不仅存在阴、阳离子间的静电作用、非极性分子间的色散作用,还存在少量的CH—N氢键和咪唑环的位阻效应。

Lonic liquids have been used as extractants in the extractive distillation processes for the separation of various alkanes and olefins due to their excellent separation properties.Molecular dynamics method was used to simulate the binary system of n-hexane and 1-butyl-3-methylimidazolium thiocyanate([BMIM][SCN]).The density and viscosity of the system were obtained.Four radial distribution functions(i.e.n-hexane-n-hexane,cation-anion,n-hexane-cation,n-hexane-anion)were used to fully analyze the microstructure of the system.The average reduced density gradient method(aRDG)was used to study the source and stability of weak interactions in the system.The results indicate that the mixture of n-hexane and[BMIM][SCN]is poorly miscible,but the mutual solubility of the two increases gradually with increasing ionic liquid concentration.There are not only the electrostatic interactions between the anions and the cations,dispersions between the non-polar molecules,but also the CH—N hydrogen bond and the steric hindrance of imidazole ring in the mixed solution.