离子液体非水溶致液晶的构建及萃取分离性能研究

发布时间：2018-06-26 02:31

本文选题：离子液体 + 非水溶致液晶　；参考：《浙江大学》2016年博士论文

【摘要】：液-液萃取是十分重要的化工分离过程。近年来,离子液体因其独特的物理化学性质而被广泛应用于液-液萃取过程,并常常表现出优于传统溶剂的萃取分离性能。然而,离子液体是由阴、阳离子组成的强极性化合物,其对极性较弱的脂溶性化合物的萃取能力受到很大限制,相应溶质的分配系数和萃取容量无法满足萃取技术发展应用的需要。本文拟利用长链羧酸离子液体兼具强氢键碱性、强亲脂性且易形成自组装结构的特点,设计构建长链羧酸离子液体非水溶致液晶新型萃取剂,建立分配系数高、萃取容量大、选择性高、萃取剂易循环的脂溶性化合物萃取分离新方法。本文合成了一系列长链羧酸离子液体,系统研究了其在非水溶剂中的自组装聚集行为,考察了阴、阳离子结构和溶剂种类对临界胶束浓度及自组装聚集结构的影响规律。研究发现,阳离子取代基较短的长链羧酸离子液体[Ch][C12OO]、[Ch][C14OO]、[N2222][C12OO]、[Emim][C12OO]和[OHemim][C12OO]能够在非水溶剂乙腈、二甲基亚砜、N,N-二甲基甲酰胺和甲醇中形成溶致液晶聚集结构,包括立方相、六角相和层状相等多类溶致液晶相态。当阳离子空间尺寸较大如[P4444]+时,溶致液晶结构消失。阴离子中烷基链的延长更有利于形成层状相溶致液晶。首次将构建的长链羧酸离子液体非水溶致液晶作为新型萃取剂应用于代表性分离对象——天然生育酚同系物的萃取分离,系统研究了离子液体阴、阳离子结构、离子液体浓度、非水溶剂种类等因素对萃取的影响规律,获得了非常高的萃取分离效率,生育酚分配系数远高于现有萃取剂,同时还具有很好的分离选择性。当生育酚原料浓度达到100mg/mL时,δ-生育酚在离子液体非水溶致液晶萃取剂中的分配系数仍然高达50-60,是同条件下常规有机溶剂、离子液体、聚合物以及不具备溶致液晶结构的离子液体/分子溶剂混合物等萃取剂的800～1000倍。采用溶剂化显色法、IR、XRD和POM等多种方法对萃取机理进行了探索。结果表明离子液体中的长链羧酸阴离子能够与目标分子发生较强的氢键相互作用,并且溶致液晶聚集结构提供了十分丰富的纳米尺度的极性/非极性微环境,两方面因素相互协同,使得目标分子增溶到溶致液晶的栅栏层,从而极大地增强了萃取剂对目标分子的萃取能力,同时保证了对目标分子的选择性识别能力。通过向萃取后的离子液体相中加入适量溶剂可以破坏溶致液晶的聚集结构,实现离子液体与目标分子的分离回收。进一步将长链羧酸离子液体非水溶致液晶萃取体系应用于长链脂肪酸、环烷酸、苯酚、苏丹红Ⅰ等典型弱酸性化合物的选择性分离过程,同样获得了很高的分离效率。对于油酸/三油酸甘油酯混合物,油酸分配系数高达400～1900,选择性系数则可高达105,实现了对油酸分子的精准识别和萃取。对于环烷酸/辛烷混合物,环烷酸在长链羧酸离子液体非水溶致液晶萃取剂中的分配系数是常规离子液体/非水溶剂复合萃取剂中的9倍以上,环烷酸对辛烷的选择性系数则在1000以上。此外,萃取剂对苯酚也表现出超高的分配系数和非常高的萃取容量,分配系数在1200以上。在上述成果基础上,进一步利用长链羧酸离子液体非水溶致液晶的有序结构及其与酚类物质的氢键作用能力,将其作为溶剂和软模板应用于氮掺杂炭材料的制备过程,成功合成了一系列不同形态的多孔氮掺杂炭材料和氮掺杂炭球。所合成多孔炭材料比表面积为252～551m2/g,氮含量为2.63～11.2 wt%,氮的形态主要为吡啶型氮和吡咯型氮。该材料对CO_2的吸附量可以达到1.8mmol/g。
[Abstract]:Liquid-liquid extraction is a very important chemical separation process. In recent years, ionic liquids have been widely used in liquid liquid extraction process because of their unique physical and chemical properties, and often show the performance of extraction and separation better than traditional solvents. However, ionic liquids are strong polar compounds formed from anion and cation, and they are weak in fat solubility. The extraction capacity of the sexual compounds is greatly limited. The distribution coefficient and the extraction capacity of the corresponding solute can not meet the needs of the development and application of the extraction technology. This paper intends to establish a long chain carboxylic acid ionic liquid nonaqueous liquid crystal by using the long chain carboxylic acid ionic liquid with strong hydrogen bond alkalinity, strong lipophilicity and easy to form a self-assembled structure. A new extraction method is established for the extraction and separation of fat soluble compounds with high distribution coefficient, high extraction capacity, high selectivity and easy circulation of extractants. A series of long chain carboxylic ionic liquids have been synthesized in this paper. The self assembly and aggregation behavior in non aqueous solvents is systematically investigated, the structure of cation and the types of solvent to critical micelle concentration are investigated. It is found that [Ch][C12OO], [Ch][C14OO], [N2222][C12OO], [Emim][C12OO] and [OHemim][C12OO], with short cation substituents, can form a lyotropic liquid crystal aggregation structure in nonaqueous solvent acetonitrile, two methyl sulfoxide, N, N- two methylformyl amine and methanol, including cubic Phase, six angle phase and layered liquid crystalline phase are equal. When the space size of the anion is larger as [P4444]+, the lyotropic liquid crystal structure disappears. The lengthening of the alkyl chain in the anion is more beneficial to the formation of the lamellar phase lyotropic liquid crystal. The non water-soluble liquid crystal of the long chain carboxylic acid ionic liquid is first applied to the representative separation as a new extractant. Object - Extraction and separation of natural tocopherol homologues, the influence rules of ionic liquid anion, cation structure, ionic liquid concentration, non aqueous solvent and other factors on extraction are systematically studied. The high extraction separation efficiency is obtained. The tocopherol distribution coefficient is far higher than that of the current extractant, and it has good separation selectivity at the same time. When the concentration of tocopherol material reaches 100mg/mL, the distribution coefficient of delta tocopherol in the ionic liquid non water-soluble liquid crystal extractant is still up to 50-60, which is 800~1000 times as much as the conventional organic solvent, ionic liquid, polymer, and the ionic liquid / molecular solvent mixture that does not have the lyotropic liquid crystal structure. The extraction mechanism was explored by coloration, IR, XRD and POM. The results showed that the long chain carboxylic acid anion in the ionic liquid could interact with the target molecules strongly, and the lyotropic liquid crystal aggregation structure provided a very rich nanoscale polar / non polar microenvironment. The two factors co operated with each other. The target molecules are solubilized to the palisade layer of the lyotropic liquid crystal, thus greatly enhancing the extraction ability of the extractant to the target molecules and ensuring the selective recognition of the target molecules. By adding a proper amount of solvent to the extracted ionic liquid phase, the aggregation structure of the lyotropic liquid crystal can be destroyed and the ionic liquid and the target can be realized. The long chain carboxylic acid ionic liquid non water-soluble liquid crystal extraction system was further applied to the selective separation process of the typical weak acid compounds such as long chain fatty acids, naphthenic acids, phenol, Sudan I and so on. The high separation efficiency was obtained. The oleic acid distribution coefficient of oleic acid / three oleate was up to 400 ~ 2. 1900, the selectivity coefficient can be as high as 105, and the accurate identification and extraction of oleic acid molecules are realized. For naphthenic acid / octane mixtures, the distribution coefficient of naphthenic acid in the long chain carboxylic acid ionic liquid non water-soluble liquid crystal extractant is more than 9 times more than that of the conventional ionic liquid / non aqueous solvent compound extractant, and the selective system of naphthenic acid to octane. In addition, the extraction agent also showed high distribution coefficient and high extraction capacity for phenol, and the distribution coefficient was above 1200. On the basis of the above results, the ordered structure of the non water-soluble liquid crystal of the long chain carboxylic acid ionic liquid and its hydrogen bond with the phenolic substance were used as the solvent and the soft mold. The plate is applied to the preparation of nitrogen doped carbon materials. A series of different forms of porous carbon materials and nitrogen doped carbon spheres have been successfully synthesized. The specific surface area of the porous carbon materials is 252 ~ 551m2/g, the nitrogen content is 2.63 to 11.2 wt%, the nitrogen form is mainly pyridine nitrogen and pyridine nitrogen. The adsorption capacity of the material to CO_2 can reach 1. .8mmol/g.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ028.32

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