含极性非质子溶剂的离子液体-kosmotropic盐双水相体系的研究

Ionic liquids (ILs) play a more and more important role in pretreatment, reaction, regeneration and hydrolysis of biomass materials and the production of high value-added chemicals. The recycling of ILs has become a key link in biological refining. Polarity aprotic solvent (PAS), a common co-solvent of ILs, can overcome high viscosity of ILs, which is helpful to improve the biomass catalytic conversion efficiency. Therefore, it is of great significance to clear the influence of PAS on the the IL recovery. However, it has been seldom reported. Based on the phase equilibrium separation theory of aqueous biphasic system (ABS), our group have confirmed that the molar volume and dipolar property of PAS affect the hydrophilicity and hydrophobicity of ionic liquid, and cause great changes of its distribution coefficient. Nevertheless, the specific rules and influence mechanism need further investigation. Therefore, this research plans to study the properties of PAS, phase behavior, phase microscopic structure and physicochemical properties, and explore the influence mechanism of PASs on IL-based ABS, with the aid of molecular dynamics and thermodynamics research. The study will provide important theoretical basis for IL-based ABS, and is of great significance to realize IL recycling.

离子液体在生物质原材料的溶解预处理、反应、再生和水解以及生产高附加值的化学品中扮演着越来越重要的角色，而离子液体循环利用也成为生物炼制中的关键环节。极性非质子溶剂能克服离子液体黏度高的缺点，有助于提高生物质催化转化效率，是离子液体常见的共溶剂。因此，明确极性非质子溶剂对离子液体分离回收的影响具有重要意义。但是，这方面的研究尚未见报道。课题组以双水相平衡分离理论为依据，已经证实极性非质子溶剂的摩尔体积和偶极性对离子液体的亲疏水性影响显著，引起离子液体在双水相中的分配系数的改变。然而，具体的规律和影响机制还需进一步探索。因此，我们拟以极性非质子溶剂的性质为主要考察因素，结合相行为、相微观结构和物化特性的研究，借助分子动力学和热力学的研究手段，探索极性非质子溶剂对离子液体双水相体系的影响机理。此研究将成为离子液体双水相分离回收提供重要理论依据，对实现离子液体的循环利用意义重大。

极性非质子溶剂作为共溶剂能够降低离子液体的黏度，有利于溶质的分散和溶解。含极性非质子溶剂的离子液体预处理木质纤维素已成为生物炼制研究领域的重要课题。为了降低离子液体带来的高成本和避免离子液体的潜在毒性所引发的环境污染，实现含极性非质子溶剂的离子液体的回收利用对推动离子液体的工业化进程具有深远意义。因此，明确极性非质子溶剂对离子液体分离回收的影响具有重要意义。本项目构建了含极性非质子溶剂的离子液体—盐四元双水相体系，离子液体回收率达到90%以上。通过考察极性非质子溶剂和离子液体的溶剂化效应参数、盐的水合吉布斯自由能、极性非质子溶剂迁移热力学参数，并结合双水相相图、系线长度、极性非质子溶剂的分配系数、离子液体的回收率以及体系的物理化学性质，明确了离子液体、盐、极性非质子溶剂和温度对离子液体-盐双水相体系的影响机理。借助热力学研究手段，观察了含极性非质子溶剂的离子液体-kosmotropic 盐双水相体系的形成过程，分析了过程中的重要参数，并很好地将模拟数据与实验数据关联起来。