Study On Molecular Basicity Regulatory Mechanism Of Ionic Liquids And Synthesis,Characterization, And Separation Performance Of Of Ionic Liquids With Strong Basicity And Good Lipotropy

Ionic liquids (ILs) show a good application prospect in the fields of acidic materials absorption and biomass transformation. Hydrogen-bond basicity of IL plays an important role in the application mentioned above. However, the relationship of ILs’structure-basicity and mechanism of basicity regulation haven’t been revealed systematically, which limits the molecure design and development for basic ILs. In addition, basic ILs reported generally have relatively strong polarity, which is negative to extractive separation of organic molecures. For these reasons, the mechanism of basicity regulation was investigated and a novel series of long chain fatty acid ionic liquids (LCFA-ILs) with strong basicity, good lipotropy and low viscosity were synthesized in this dissertation.The relationship of ILs’cation-anion interaction and basicity systematically as well as or group-tethered position was investigated by adopting quantum chemical calculation methods at the electronic level. Two quantum-chemical parameters, the most negative surface electrostatic potential and the lowest surface average local ionization energy, were uesd as powerful tools to demonstrate the electrostatic and covalent aspects of basicity, respectively. It was found that when the cation-anion interaction engery of ILs was decreased, both of the electrostatic and covalent basicity of anion in ILs enhanced remarkly. Furthermore, when the amino group was tethered to the anion, the basicity of group was much stronger than that of the cation-tethered ILs. Hence, two ways to enhance the ILs’basicity were proposed:by weakening the cation-anion interaction and by employing the anion-tethered strategy.13kinds of novel ILs with strong basicity and good lipotropy (named LCFA-ILs) were synthesized for the first time, by introducing long chain fatty acid (carbon number:8～20) with flexible structure to anion part of ILs. And their properties, including the hydrogen-bond basicity/β, dipolarity π﹡, viscosity, melting point, glass transition temperature and thermal decomposition temperature were characterize. The results demonstrated that the LCFA-ILs achieved one of the highest β values (β=1.55～1.65,60℃) ever reported. In addition, LCFA-ILs showed a lower π*(0.76～0.86,℃), also good lipotropy, lower viscosity (381.00～488.57cP,25℃) and good thermal stability (TD>210℃). The separation performance of the LCFA-ILs synthesized was preliminarily studied in the process of extraction of representative acdic organic molecules. By cation structure changed, LCFA-ILs could form two kinds of two-phase system: ILs-water, ILs/diluent-hexane. Moreover, LCFA-ILs showed relatively strong ability to extraction of organic molecules. For instance, the distrubition coefficient of LCFA-ILs to phenol was up to736.6, which was42times of the [Omim][PF6].