| The separation of natural bioactive homologues is the key process in the valorization of natural bioactive compounds, but current separation methods such as the adsorption chromatography technology have problems such as low capacity, large solvent consumption and significant energy consumption. Based on the unique properties of ionic liquids (ILs) such as task-specific tunability and good ability to form liquid-liquid biphasic systems, a novel method for the selective separation of natural bioactive homologues, mediated by ILs through liquid-liquid extraction process, has been described by this dissertation. Also, through the highly selective separation of tocopherol homologues and isoflavone homologues, the great potential of this method in actual applications has been demonstrated.In this dissertation, quantum chemical methods were employed to investigate the structure and properties of tocopherol homologues and ILs, and the interaction mechanism between tocopherols and ILs. It was found that the hydrogen-bond acidity of each kind of tocopherol is different, and the selective separation of tocopherol homologues could be realized by the different hydrogen-bonding interaction of IL with different tocopherol homologues. This interaction could be influenced by the structure of IL, therefore the separation efficiency could be finely adjusted by the change of ILs.The physicochemical properties of IL-molecular solvent binary mixtures were studied. The viscosity of mixture would exponentially decrease with the increase of mole fraction of molecular solvent. The Kamlet-Taft solvatochromic parameters, including dipolarity/polarizability, hydrogen-bonding basicity and hydrogen-bond acidity, could be further adjusted by the kind and amount of molecular solvent finely. Therefore, a novel strategy using IL-molecular solvent as multiple extractant was proposed in this dissertation. The employ of multiple extractant can not only overcome the drawback, i.e. the large viscosity, of IL, but also expand the variety and selectability of extraction medium.Based on the research result of quantum chemical calculation and the molecular characteristics of tocopherol homologues, a series of IL-hydrophobic solvent or IL-hydrophilic diluent-hydrophobic solvent biphasic systems with different physicochemical properties and low mutual solubility were established. The relationship between the structure and property of IL and tocopherol and the distribution coefficient and selectivity of tocopherol homologues were investigated, and the highly selective separation of tocopherol homologues was realized successfully. Through the synergetic effect of IL and diluent together with the double adjustment by them, a good match could be achieved between the distribution coefficient of tocopherols and the selectivity of different homologues, as well as decreased consumption of ILs. While using the [bmim]Cl-acetonitrile mixture with a mole fraction of 2% as extractant, in the biphasic system constituted by it with hexane at 30℃, the selectivity ofδ-tocopherol to a-tocopherol was 11.3, four times larger than that using pure acetonitrile as extractant. The distribution coefficients ofδ-,β&γ-, and a-tocopherol were 4.07,2.02 and 0.36 respectively, which were at least eighteen times larger than those using pure [bmim]Cl as extractant.Sulfonic acid-functionalized ILs with different structures were synthesized, and they were used as novel catalysts for the hydrolyzation of soybean isoflavone glycosides. Good catalytic activity was found, and the high-level mixture of soybean isoflavone aglycon homologues was produced. Then, based on the physicochemical characteristics of soybean isoflavone aglycon homologues, hydrophobic IL-water biphasic system was designed and the extractive separation of soybean isoflavone aglycon homologues was achieved with high selectivity. The selectivities of genistein to daidzein or glycitein were both larger than 3.
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