温敏木质素凝胶的制备及其吸附分离生物丁醇的性能和机理研究

Biobutanol is considered as a very promising clean fuel. The very low concentration of butanol obtained from fermentation causes the high energy consumption for its separation, which is the bottleneck of its development. Lignin, as byproduct in biobutnanol industry, is proposed to prepare gel for biobutanol adsorption and separation in this programme, in order to obtain the higher concentration for butanol. Not only it could reduce the energy consumption for biobutanol separation, but also could it improve the utilization of lignin. First, the research method for the mechanism and structure-function relationship is taken by using lignin fractions of different solubleness as the entry point, to resolve the difficulty caused by the complex structure of lignin. Then, regulate the molecular structure of lignin by directed hydrophilic modification to improve the specific surface area. So, there would be more adsorption sites for the effective contaction between lignin and butanol. Third, improve thermosensitivity of lignin gel by taking PNIPAM. By this method, the free water could get in and out of the gel controllably at normal temperature. Thus, energy consumption for the phase-transition of water can be obviously reduced. At the theoretical level, the adsorption mechanism and structure-function relationship would be illuminated. The mechanism of temperature effect on the interactions between lignin and butanol would be revealed. The adjustment and control of structure method for the lignin gel would be developed. And the adsorption model would be build. This programme could lay a solid theoretical foundation for the research of lignin-based thermosensitivity adsorption gel and its use for biobutanol separation.

生物丁醇作为极具前景的清洁可再生能源得到广泛关注。利用发酵法得到的丁醇产物浓度很低，导致后续精馏分离能耗极高，成为生物丁醇产业发展的瓶颈。本项目以丁醇产业副产的木质素为原料制备温敏凝胶用于吸附富集发酵液中的丁醇以得到高浓度浓缩液，在降低分离能耗的同时合理利用木质素资源，实现物尽其用。首先以溶解分级为切入点建立研究木质素吸附构效关系的新方法，解决其复杂结构而不易研究的难题；进而通过定向亲水修饰打破木质素的聚集体结构，促进吸附位点与丁醇的有效接触以提高吸附容量；最后在制备凝胶时引入PNIPAM强化木质素温度响应性，实现凝胶内自由水在常温下的可控出入以降低热脱附能耗。在理论上阐明木质素吸附丁醇的作用机制及构效关系，揭示丁醇在木质素上的吸附量随温度出现拐点的原理，发展木质素吸附凝胶的结构调控方法，建立吸附分离模型。本项目的成功实施可为温敏木质素吸附凝胶的制备及其在分离生物丁醇中的应用奠定理论基础。

生物丁醇作为极具前景的清洁可再生能源得到广泛关注。利用发酵法得到的丁醇产物浓度很低，导致后续精馏分离能耗极高，成为生物丁醇产业发展的瓶颈。本项目首先以丁醇产业副产的木质素为原料制备温敏凝胶用于吸附富集丁醇，在降低分离能耗的同时合理利用木质素资源。在此基础上，为进一步提高整个分离流程的效率并降低能耗，拓展了盐析萃取、特殊精馏等其他方法在分离丁醇及其他类似低浓度生物发酵产物过程中的相关研究。与此同时，基于研究过程中对生物质大分子结构复杂的认识，还进一步探索了利用离子液体催化降解木质素和纤维素的相关基础研究。.通过研究，揭示了π-π、氢键以及范德华力等对木质素对丁醇的吸附作用机制，明确了苯环和羟基等对丁醇的协同吸附效应，通过引入N,N-二乙基丙烯酰胺制备出了具有温度响应特性的木质素温敏凝胶，实现了低浓度丁醇的高效富集。研究还发现利用溶解分级得到的木质素对小分子吸附性能产生显著差异的原因不仅源自化学结构的差异，更重要的是源自不同木质素在溶液中聚集体内部孔道结构的显著。在木质素凝胶制备过程中引入亲水基团可使木质素在溶液中的聚集体结构打开而使得疏水位点得以充分暴露，强化吸附质在木质素周围的传递行为，可显著增强吸附效果。研究还发现盐析过程对分离生物丁醇亦具有很好的适用性，并进一步地拓展应用到了对乙偶姻、2,3丁二醇等其他低浓度生物发酵产物的提取。为较全面地研究低浓度物系的分离方法，进一步研究了热耦合精馏过程强化手段，提出了外部热集成的多级非绝热塔结构概念和相应的严格计算模型，为新型热集成精馏设备的工业设计以及应用提供理论基础。上述相关方法为低浓度溶液中有机物的高效提取奠定了科学基础。此外，根据离子液体可设计性强的特点，利用量子化学理论设计并筛选出降解木质素、纤维素的催化剂，提出了双功能化离子液体的分子设计思路，实现了温和条件下高效绿色转化生物质为高附加值小分子的目标。