微波驱动水解中再生纤维素再次结晶的机理及抑制方法研究

On basis of hydrolysis of cellulose, by through synthesis of platform chemicals and then preparation of bio-based polymers, there forms an important way to achieve high-quality utilization of cellulose resources with an annual output over 100 billion tons, which is of great strategic significance to maintain the sustainable development of polymer materials industry in the future, to save petrochemical resources and to build a "carbon neutral" cycle. The transition from cellulose to regenerated cellulose by through “dissolution and regeneration” and then the hydrolysis of regenerated cellulose into sugar driven by microwave irradiation is reported in recent years as the optimal technical strategy of “two-step” hydrolysis. However, that the regenerated cellulose is prone to re-crystallization, which leads to the decrease of ability of hydrolysis, becomes the key point to restrict the efficiency of hydrolysis to sugar. Aim at the unclear mechanism of the re-crystallization of regenerated cellulose, this proposal puts forward the use of the hydrolysis method driven by microwave irradiation with synchronous cooling to accurately control the thermal effect and non-thermal effect of microwave, together with combination of the control of hydrolysis system, and then systematically investigate the ability, speed and type of the recrystallization of regenerated cellulose, after that tries to clarify the mechanism of re-crystallization of regenerated cellulose. After that, under the guidance of the theory, by through the formation of the system of hydrolysis, a targeted inhibition of the re-crystallization of regenerated cellulose is tried to find out, and thus the high efficient hydrolysis to sugar is achieved. This study will provide an important theoretical and technical foundation for the high efficiency and high-quality utilization of cellulose.

以纤维素水解成糖为基点，经平台化合物制备生物基高分子材料，是实现年产超千亿吨纤维素资源高质化利用的重要途径，对维系未来高分子材料产业的可持续发展、节约石化资源、构建“碳中性”循环，具有极其重要的战略意义。将纤维素经“溶解、再生”转化为低结晶度的再生纤维素，而后在微波驱动下水解成糖，是近年来报道综合效果最优的纤维素“两步法”水解成糖技术策略。然而，再生纤维素容易发生再次结晶，导致水解能力降低，成为制约水解成糖效率提升的关键要点。针对再生纤维素再次结晶机理不清的问题，本项目提出利用带有同步冷却的微波驱动水解方法，准确控制微波热效应及非热效应，结合水解体系调控，系统考察再生纤维素在的再次结晶能力、速度与类型，试图阐明再生纤维素再次结晶机理。并在该理论指导下，通过水解体系组建，针对性找出再生纤维素再次结晶的抑制方法，实现高效水解成糖。此项研究将为纤维素的高效高质利用提供重要的理论技术依据。

本项目主要围绕再生纤维素在微波驱动水解中产生再次结晶及其抑制方法开展研究，通过对再生纤维素再次结晶行为的抑制提升其在全水相体系中的水解成糖响应能力及效率，为推动纤维素向生物基能源、材料的高质高效转化利用奠定理论技术基础。在研究中，首先通过同步冷却速度的调控，考察了微波给波强度及功率对再生纤维素分子链上羟基间氢键作用的能力与程度，同时结合再生纤维素水解残余物结晶结构及水解成糖效率的变化，系统解析了再生纤维素在微波驱动水解过程中再次结晶的行为，由此掌握了利用纤维素分子链上羟基的松弛调控促进其水解能力与效果提升的原理和方法。而后，成功构建出含ZrO2的全水相低酸体系，在水解过程中实现了对再生纤维素再次结晶的有效抑制，在水相体系中激发了纤维素的高效水解响应及成糖转化。通过系统揭示ZrO2结构形貌对再生纤维素水解促进的能力与作用，找出了实施再生纤维素高效水解成糖的条件。在全水相低酸体系中，经15min微波驱动反应后，再生纤维素的转化率和水溶性糖产率分别达到98.4±0.5%及97.9±0.6%。通过简单的分离纯化方法，成功实现了纤维素水解液中糖产物的分离提取，并利用酵母发酵实现了纤维素糖产物向乙醇的转化。与市售商品化的葡萄糖相比，纤维素水解糖产物具有同样良好的发酵制备乙醇的能力。