新型咪唑离子液体的合成及其对纤维素溶解性能的研究

发布时间：2018-04-23 11:37

  本文选题：离子液体 + 纤维素　； 参考：《福建农林大学》2017年硕士论文

【摘要】：离子液体作为"绿色"溶剂,在溶解纤维素方面的研究取得了很大进展,但第二大天然高分子材料——壳聚糖在离子液体中的溶解研究还鲜有报道,并且现有离子液体存在熔点高、黏度高、稳定性差等缺点。因此,开发新型高效并且对纤维素与壳聚糖都具有良好溶解能力的离子液体成为必然趋势。本文通过分子动力学模拟以及溶剂化显色参数等手段,研究极性非质子溶剂与[AMIM]C1对纤维素的协同溶解作用,探讨纤维素在离子液体中的可能溶解机理,为新型离子液体的合成提供理论指导。在此基础上,设计合成了一种新型咪唑醋酸盐离子液体,系统地研究了该离子液体的结构、物理化学性质、对纤维素及壳聚糖溶解性能以及回收等工作。主要内容包括:首先,采用分子动力学模拟、溶剂化显色参数等手段研究了离子液体[AMIM]C1与极性非质子溶剂二甲基亚砜(DMSO)、N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAC)以及乙腈(ACN)组成的二元体系对纤维素的溶解过程,探究了[AMIM]Cl[AMIM]C1及有机溶剂复配体系对纤维素的溶解机理;结果表明,极性非质子有机溶剂的加入可提高离子液体对纤维素的溶解能力。纤维素的溶解度会随混合体系中极性非质子有机溶剂含量的增加先增大后减小,其中[AMIM]C1/DMSO体系在质量比为3:1时的溶解效果最佳。再生后的纤维素晶型由I型变为II型,且热稳定性下降。其次,设计合成了一种带有双烯丙基的咪唑醋酸盐离子液体——1,3-二烯丙基-2-乙基咪唑醋酸盐。采用FT-IR、HNMR对其分子结构进行表征,分析了新型离子液体的物理化学性质及对纤维素、壳聚糖的溶解性能;结果表明,含有两个烯丙基的离子液体会发生共轭效应,其电导率高于含有单个烯丙基的离子液体。该离子液体对纤维素和壳聚糖具有良好的溶解能力,并可同时溶解纤维素与壳聚糖,纤维素由I型变为II型,壳聚糖由α型变为β型。同时探索了极性非质子溶剂(DMSO)的加入对新型离子液体溶解能力的影响。结果表明,DMSO的加入会促进1,3-二烯丙基-2-乙基咪唑醋酸盐离子液体对纤维素的溶解,且在离子液体与DMSO的质量比为3:1时,其溶解效果最佳。但DMSO的加入会阻碍壳聚糖在1,3-二烯丙基-2-乙基咪唑醋酸盐离子液体中的溶解。最后,使用活性炭吸附回收离子液体,研究了活性炭对离子液体1,3-二烯丙基-2-乙基咪唑醋酸盐的吸附效果,考察了活性炭用量、离子液体浓度、吸附温度、吸附时间以及活性炭使用次数对吸附性能的影响,探究无机盐硫酸钠的添加对吸附过程的影响。结果表明,当活性炭用量8g/L,硫酸钠用量240g/L,温度30℃左右,吸附时间2h的条件下,活性炭对质量浓度为80 mg/L的1,3-二烯丙基-2-乙基咪唑醋酸盐水溶液的吸附率可达到99%以上,再生回收率可达93%。硫酸钠的加入能促进离子液体与水相的分离,提高活性炭对离子液体的吸附效果。
[Abstract]:As a "green" solvent, ionic liquids have made great progress in the dissolution of cellulose, but the dissolution of chitosan, the second largest natural polymer material, in ionic liquids has not been reported. And the existing ionic liquids have the shortcomings of high melting point, high viscosity and poor stability. Therefore, it is an inevitable trend to develop new ionic liquids with high efficiency and good solubility to cellulose and chitosan. In this paper, the synergistic dissolution of cellulose by polar non-proton solvent and [AMIM] C1 was studied by means of molecular dynamics simulation and solvation coloration parameters, and the possible dissolution mechanism of cellulose in ionic liquid was discussed. It provides theoretical guidance for the synthesis of new ionic liquids. On this basis, a new imidazole acetate ionic liquid was designed and synthesized. The structure, physical and chemical properties, solubility of cellulose and chitosan and recovery of the ionic liquid were systematically studied. The main contents are as follows: first, molecular dynamics simulation is used. The dissolving process of cellulose in the binary systems composed of ionic liquid [AMIM] C1 and polar non-proton solvent DMSO-N- (N-dimethylformamide) and acetonitrile (acetonitrile) has been studied by means of solvation coloration parameters, and the results are as follows: (1) the solubility of cellulose in the binary system composed of [AMIM] C1 and dimethyl sulfoxide dimethyl sulfoxide (DMSO), a polar non-proton solvent, has been studied. The dissolution mechanism of cellulose by [AMIM] Cl [AMIM] C1 and organic solvent was studied, the results showed that the solubility of ionic liquid to cellulose could be improved by adding polar non-proton organic solvent. The solubility of cellulose increases at first and then decreases with the increase of the content of polar non-proton organic solvent in the mixed system. The solubility of [AMIM] C1/DMSO system is the best when the mass ratio is 3:1. After regeneration, the crystalline form of cellulose changed from type I to type II, and the thermal stability of the regenerated cellulose decreased. Secondly, a diallyl imidazole acetate ionic liquid was designed and synthesized. The molecular structure was characterized by FT-IRN HNMR, the physical and chemical properties of the new ionic liquids and their solubility to cellulose and chitosan were analyzed, the results showed that conjugation effect occurred in ionic liquids containing two allyl groups. Its conductivity is higher than that of ionic liquids containing a single allyl group. The ionic liquid can dissolve cellulose and chitosan at the same time. Cellulose changes from type I to type II and chitosan from type 伪 to type 尾. At the same time, the influence of the addition of polar non-proton solvent (DMSO) on the solubility of new ionic liquids was investigated. The results show that the addition of DMSO can promote the dissolution of cellulose by ionic liquids of 1 ~ 3-diallyl -2-ethylimidazolium acetate, and the dissolution effect is the best when the mass ratio of ionic liquid to DMSO is 3:1. However, the addition of DMSO hinders the dissolution of chitosan in 1: 3-diallyl-2-ethyl imidazole acetate ionic liquids. Finally, the adsorption effect of activated carbon on ionic liquid (1) 3-diallyl -2-ethylimidazole acetate was studied. The amount of activated carbon, the concentration of ionic liquid and the adsorption temperature were investigated. The influence of adsorption time and times of activated carbon on adsorption performance and the effect of addition of inorganic salt sodium sulfate on adsorption process were investigated. The results show that when the amount of activated carbon is 8g / L, the amount of sodium sulfate is 240g / L, the temperature is about 30 鈩，

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