Computer-aided Selection Of Ionic Liquid As Solvent In Industry

As the society advances, people have stronger environmental awareness. Since most of the traditional organic solvent are bad for the environment, to seek a new kind of green solvent become more urgent. Room-temperature ionic liquid is a new kind of green solvent. It is environmental with low saturation vapour pressure, stable chemical properties, big electrochemical window and easy recovery compared with traditional organic solvent. In the aspect of solubility, many solute have good solubility in ionic liquids, it is urgent to explore the dissolution mechanism. At present, most studies are about the solubility of aromatic hydrocarbon, alcohol and some polar compounds in ionic liquids, while few are on cycloalkanes, alkane or polymer. This research explore the structure and dynamic properties of benzene, cyclohexane and hexane in different ionic liquids as well as the reasons that lead to the upper critical solution temperature of poly(N-isopropylacrylamide)(PNIPAM) in ionic liquid,1-ethyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)amide([EMIM][NTF2]), the mainly contents and results are as follows:Firstly, we used molecular dynamics simulation to study the structure and dynamic properties of different concentration of benzene in 1-butyl-3-methylimidazolium hexafluorophosphate([BMIM][PF6]) at different temperatures. The results proved that the temperature hardly influence the interaction between anion and cation, but the diffusion coefficient of anion and cation enlarge as the temperature goes up, the higher temperature, the smaller growth rate. The diffusion coefficient of anion and cation enlarge as benzene put into the ionic liquid, because the interaction between anion and cation became weaker, and the higher concetration, the smaller growth rate. As the concentration of benzene enlarges, the interaction between anion and cation of [BMIM][PF6] becames weaker, so does the interaction between benzene and anion or cation, benzene and benzene appear gathered phenomenon. Relatively speaking, the interaction between benzene and anion of hydrophobic ionic liquid was stronger, the interaction between benzene and cation of hydrophobic ionic liquid was weaker.Then we studied the structure and dynamic properties of benzene, cyclohexane and hexane in [BMIM][PF6], 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM][BF4]), 1-butyl-3-methylimidazolium chloride([BMIM][Cl]) as well as 1-butyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)amide([BMIM][NTF2]) respectively. After the organics have been put into the ionic liquid, the interaction between the anion and the cation in [B MIM][PF6], [BMIM][BF4] and [BMIM][NTF2] became weaker, while the interaction between anion and cation in [BMIM][Cl] became stronger. In addition, all of the diffusion coefficient of anion and cation in the four ionic liquids became bigger. Besides, the interaction between bezene, cyclohexane, hexane and Cl-, BF4-, PF6-, NTF2- becames bigger and bigger. Meanwhile, the interaction between benzene, cyclohexane, hexane and the cation of hydrophilic ionicliquid([BMIM][BF4], [BMIM][Cl]) were bigger than hydrophobic ionic liquid([BMIM][PF6], [BMIM][ NTF2). Within the distance less than 1.2nm, the number of anion and cation of [BMIM][Cl], [BMIM][BF4], [BMIM][PF6], [BMIM][NTF2] around solute increases orderly. It was maybe related to the radius of ionic and the interaction between organics and ionic liquid. Combining the position related functions of ions around solute with solubility parameter, we knew cyclohexane had better solubility in [BMIM][PF6], and benzene had better solubility in [BMIM][NTF2].Finally, we studied the structure and dynamic properties of PNIPAM in [EMIM][NTF2] at 373.15 K. We found the hydrogen of imidazole ring arrange more closely than other hydrogen. It was much more cations than anions around amido bond of PNIPAM, the cations, anions around amido bond was more stable than around backbone and isopropyl. Besides, we found the imino group of PNIPAM could form hydrogen bonds with the oxygen, fluorine of anion, but the stability of hydrogen bonds were not very well.Thus, the upper critical solution temperature of PNIPAM in [EMIM][NTF2] had great relationchip with the amido bond of PNIPAM.