| The amino-functionalized ionic liquids, owing to their strong basicity, have potential applications in the areas of CO2capture and organic compounds extraction. The high CO2absorption capacity of amino-functionalized ionic liquids has been reported, but the mechanism hasn’t been fully elucidated yet, which seriously hinders the exploration of new ILs. The mechanism of CO2absorption in amino-functionalized ionic liquids was studied in this thesis by experimental and simulation methods. Based on the reversible CO2chemical absorption, a new method of solutes recovery from ionic liquid phase by back extraction was developed.The CO2absorption capacities in11amino acid ionic liquids were determined and the effects of the ionic liquid structure, the absorption temperature and the cosolvent on the capacities of CO2were studied. High CO2capacities were obtained by amino acid ionic liquids, e.g.,[P66614][Met] and [P66614][Pro] have reached the equimolar CO2absorption (1mol CO2/mol IL). Herein, we have developed a practical method for the quantitative analysis of the CO2absorption mechanism in amino acid ILs for the first time. The results indicated that even the equimolar CO2absorption has a multiple absorption mechanism, includes1:1mechanism (contributes0.36-0.56mol CO2/mol IL) and1:2mechanism (contributes0.22-0.32mol CO2/mol IL), both absorbed by amino group, and CO2chemical absorption mechanism by COO-group (contributes0.13-0.21mol CO2/mol IL). The CO2absorption mechanism has been strongly affected by the anion structures. For the [Pro]-ionic liquids, the CO2absorption is mainly followed by the1:1mechanism. The ratio of1:1absorption increases with the increase of the size of cations and the decrease of interaction between anion and cation.The quantum chemical methods were employed to investigate the CO2absorption in amino acid ionic liquids. In order to design ionic liquids with high CO2capacity, the quantum chemical methods was used to investigate the absorption mechanism. The results indicate that the enthalpy of proton dissociation from carbamic acid (E2) is the key factor of CO2absorption. The ratio of1:2CO2 absorption decreases with the increase of E2. The enthalpy of proton dissociation (E2) is influenced by two factors:1) E2increases with the increase of the basicity of amino group in the anion of ionic liquids,2) The increase of stability of carbamate dianion generated by the proton dissociation reaction results in the increase of E2. For example, the [Pro]-in ionic liquids has a strong basicity and unique five-membered heterocyclic structure, which can increase the stability of carbamic acid and lead to1:1mechanism CO2absorption.The effect of CO2to the extraction of acidic natural products by amino acid ionic liquids is reported for the first time. How the structure and property of ILs, cosolvents, extraction temperature, the concentrations of ionic liquids and solutes affect the distribution coefficients were investigated. For the extraction of tocopherols, it was found that CO2can obviously decrease the distribution coefficients, which was good for the back extraction of tocopherols. The decrease of distribution coefficient was affected by the structure of ILs and the types of cosolvents, e.g., the distribution coefficients of8-tocopherol in [P4444][Pro] and [Bmim][Ac] could be reduced from6.45and9.57to2.02and1.45, respectively. A new method of CO2assisted solutes back extraction from ionic liquid phase was developed based on the reversible CO2absorption. For the tocopherol extraction, the existence of CO2can lead to the less extraction operation stages and less hexane consumption. For example, for the a-tocopherol back extraction from [P4444][Pro]-DMSO phase, with the existence of CO2, it needs only2times back extraction operation to reach90%recovery, and80%of hexane is reduced. The back extraction with CO2is suitable for many acidic solutes such as sudan I and phenol. The back extraction with the existence of CO2is expected to become a new green and efficient method in ionic liquids extraction. |
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