基于酸性离子液体溶解/催化双重作用的甲壳素/壳聚糖绿色转化制备5-羟甲基糠醛及其反应机理研究

5-Hydroxymethylfurfural(5-HMF) is an important platform chemical，which can be transfered to the biofuels by the next reaction. The production of 5-hydroxymethylfurfural, wich is obtained directly from chitin/chitosan would solve the resourse and energy crisis. Regarding this problem chitin/chitosan conversion to 5-HMF，namely chitin/chitosan is difficult to be dissolved and can not be hydrolyzed completely, catalytic efficiency of Lewis acids was low and the catalysts can not be reused and often resulted in environmental pollution. According to the degradation characteristics of chitin/chitosan in acidic solution and the demand of environmental protection and economy, we plan to synthesize new environmental friendly, low-cost acidic ionic liquids using renewable resources as raw materials. With the acidic ionic liquid as solvent and catalyst, we research the rules of green degradation of chitin/chitosan and explore the impact of ionic liquids structure and reaction conditions on the conversion. The effect of structure of the ionic liquid on hydrolization of chitin/chitosan into glucosamine and isomerization of glucosamine into 5-HMF were studied so as to reveal the conversion mechanism. Finally we establish a new chitin/chitosan conversion system which can degrade chitin/chitosan into 5-HMF efficiently in a green way. This provides a scientific basis for the application and development of ionic liquids in the field of the chitin/chitosan degradation.

5-羟甲基糠醛（5-HMF）是一种重要的化工平台化合物, 可经过进一步反应生成燃料。从可再生资源如甲壳素/壳聚糖制备5-HMF是解决资源和能源危机的重要方法之一。针对现有甲壳素/壳聚糖降解制备5-HMF的体系存在甲壳素/壳聚糖难溶解、水解不完全，以及Lewis酸催化效率低、不能循环使用、带来环境污染等问题。本课题根据甲壳素/壳聚糖能在酸性溶液中降解的特点，本着环保与经济的要求，拟以再生资源为原料合成新型环境友好、成本低的酸性离子液体，研究其作为溶剂和催化剂在甲壳素/壳聚糖降解制备5-HMF的反应规律，探索酸性离子液体结构及反应条件对甲壳素/壳聚糖降解效率的影响，揭示该离子液体结构在甲壳素/壳聚糖水解为氨基葡萄糖、氨基葡萄糖异构化脱水制5-HMF反应中的作用机理，实现一锅法绿色高效降解甲壳素/壳聚糖制备5-HMF, 为丰富和发展离子液体在甲壳素/壳聚糖降解领域的应用提供科学依据。

甲壳素/壳聚糖是地球上仅次于纤维素的第二大可再生生物资源，把甲壳素/壳聚糖转变为高附加值的燃料和化学品，符合可持续发展的战略和国家节能与环保的要求，具有巨大的经济价值。本项目将制备环境友好、成本低、溶解能力强、催化效率高的酸性离子液体，实现酸性离子液体中甲壳素/壳聚糖“一锅法”降解转化制备5-HMF。以期找到低碳、低能耗、绿色的甲壳素/壳聚糖降解转化制备5-HMF的技术路径，为酸性离子液体在甲壳素/壳聚糖降解领域的应用及其后续研究提供理论基础。通过本项目的资助，代表性研究成果主要包括：1、合成了一系列环境友好的酸性离子液体，包括咪唑类、噻唑类、季铵盐类、苯并咪唑类Brønsted-Lewis双酸性离子液体，并测试了其结构和酸性。2、1-羧甲基-3-甲基咪唑氯盐[HOOCMMIM]Cl离子液体能有效地溶解壳聚糖，测试了其溶解性能。3、酸性离子液体[HMIM]HSO4在不同的溶剂中对壳聚糖和N-乙酰氨基葡萄糖的降解性能不同，加入DMSO会对降解产生重大的影响。研究了溶剂、温度、催化剂的量对降解性能的影响，并探索了其降解的机理。4、Brønsted-Lewis双酸性离子液体[Hmim][HSO4]- 0.5 FeCl2能有效降解壳聚糖转变为5-HMF，优化了反应条件，并提出了壳聚糖降解的机理。5、研究了1-羧甲基-3-甲基咪唑氯盐和苯并咪唑氯盐能有效催化壳聚糖降解制备高附加值化学品5-羟甲基糠醛。为壳聚糖的溶解和降解，转化制备高附加值化学品5-HMF提供了重要的参考依据。