【作者】 黄科林；

【导师】 王金淑；

【作者基本信息】 北京工业大学 ， 材料学， 2013， 博士

【摘要】 随着石油、煤等不可再生资源的日益枯竭，以可再生物质特别是废弃生物质为原料制备高附加值化工产品逐渐成为人们研究热点。我国是世界上甘蔗产量的第三大国，其中广西是我国种植和生产甘蔗糖的最大省份，近年来广西的甘蔗产量均占全国总产量的60%以上。甘蔗榨糖的副产物为甘蔗渣，由于甘蔗渣中含有大量的纤维素，因此充分利用可再生的甘蔗渣纤维素生产高附加值的纤维素衍生物不仅具有很高的学术价值，也有很大的经济效益和社会效益。本文研究了在非常规介质中利用蔗渣纤维素制备高附加值的材料，包括使用近临界水/CO₂非常规介质制备出高纯度微晶纤维素，并以制备的微晶纤维素为原料，在新型绿色溶剂离子液体中一步清洁制备高附加值的纤维素有机酯，同时实现离子液体溶剂的循环利用。整个工艺过程高效、清洁，真正实现了从甘蔗渣纤维素到微晶纤维素再到纤维素酯的全过程绿色转化。主要研究成果如下：利用近临界水/CO₂二元体系中具有较高H+浓度、较低介电常数和粘度、较大扩散系数及较高温度的特性，本文以蔗渣纤维素为原料首次在近临界水/CO₂中降解制备蔗渣微晶纤维素（SBMC），避免了传统酸水解工艺中污染较严重、反应时间长等缺陷，通过研究得到最佳工艺条件为：反应温度为200℃，反应时间为60min，液固比为40:1，反应初压力为2MPa。在此条件下，SBMC的聚合度为215。通过表征表明蔗渣纤维素在降解过程中仅仅发生苷键的断裂，没有发生晶型的改变。所得的SBMC呈现短棒状结构，分子量分布较传统工艺均一，结晶度为74%，最初分解温度为308.3℃，粒径140目以上占87.2%，体积密度和拍实密度分别为0.32g/cm3和0.42g/cm3。以烯丙基氯和N-甲基咪唑为原料，制备出1-烯丙基-3-甲基咪唑氯盐（AmimCl）离子液体。所得的AmimCl离子液体具有良好热稳定性及流动性，初始分解温度为270℃，粘度和密度分别为1179mPa·s和1.1438g/cm3。同时，所制备的微晶纤维素在离子液体中能够直接快速的溶解，在80℃、1h内形成完全均匀的溶液，远优于纤维素在离子液体中的溶解效果。这是由于微晶纤维素较纤维素聚合度低，分子量分布更均一，更易溶解。以自制的蔗渣微晶纤维素为原料，在无催化剂加入条件下，在AmimCl离子液体中一步制备出醋酸纤维素（CA，取代度为0.71².92）、醋酸丙酸纤维素（CAP，丙酰基含量为24.4⁴7.7%，乙酰基含量为1.7¹0.3%）和醋酸丁酸纤维素（CAB，丁酰基含量为27.5⁵2.8%，乙酰基含量为1.7⁹.7%）三种纤维素酯类产品。研究发现，均合成了指定结构的纤维素酯产品，酰基取代首先发生在C6位；醋酸纤维素、醋酸丙酸纤维素和醋酸丁酸纤维素初始分解温度随酰基碳链的延长而降低，分别为353℃、346℃和341℃；结晶度分别为37.0%、33.9%和47.5%；特性粘度随纤维素酯分子量增大分别以1.00mL·g^-1、3.00mL·g^-1和5.00mL·g^-1呈递增趋势；三种酯分别在二甲基亚砜、丙酮、丁酮等溶剂中具有良好的溶解性能。为更好控制反应条件，掌握离子液体中微晶纤维素酯化反应规律，研究了微晶纤维素在离子液体中均相酯化反应动力学。研究发现，纤维素在离子液体中均相乙酸酐酯化和混酐酯化均为1级反应，乙酸酐酯化反应的活化能为17.70kJ·mol^-1，酯化反应的反应速率表达式为Rg=3.15×10^-2e^-17700/RT[MCC]1.0[Anhydl]^0.04(mol·L^-1·s^-1)；混酐酯化反应的活化能为20.30kJ·mol^-1，酯化反应的反应速率表达式为Rg=9.94×10^-2e^-20370/RT[MCC]^1.0[Anhydl]^0.039[Butyryl]^0.038(mol·L^-1·s^-1)。鉴于分子蒸馏是依靠不同物质分子逸出后的平均自由程的差别来实现物质的分离，具有分离程度高、温度低等特点，本文采用分子蒸馏技术，对微晶纤维素发生酯化反应后离子液体进行回收并循环利用。研究发现，纤维素乙酸酐酯化反应后离子液体回收的最佳工艺条件为：进料速率2mL/min、蒸馏温度95℃、刮膜转速413rpm、蒸馏压力0.1Torr；微晶纤维素混酐酯化反应后离子液体废液分子蒸馏的最佳工艺条件为：进料速率2mL/min、蒸馏温度110℃、刮膜转速413rpm、蒸馏压力0.1Torr。得到5次回收-循环利用所得离子液体（RIL）的含量都在99.5%以上，而且与新鲜离子液体（FIL）相比，外观、结构等同新鲜离子液体（FIL）相差不大；同时，得到在相同条件下，利用回收的离子液体循环制备的醋酸纤维素及醋酸丁酸纤维素与新鲜离子液体所得产品相比较，外观、粘度、取代度、结构等性质都十分相近。更多还原

【Abstract】 With the oil, coal and other non-renewable resources exhausted gradually, thepreparation of high value-added chemical products from renewable biomass, speciallythe waste biomass, has become a hot topic in the field of biomedical. The sugar caneproduction of China is the third largest country in the world and the Guangxi provincehave largest output, which accounts for60percent of national output of sugar cane inrecent years. Sugarcane bagasse （SB） is the byproduct of sugar cane sugarmanufacture, which contains a lot of cellulose. Therefore, it is significant to make fulluse of sugarcane bagasse cellulose （SBC） to produce high value-added cellulosederivatives products, not only the high academic value, but also the great economicand social benefits. In this paper, high purity sugarcane bagasse microcrystallinecellulose（SBMC） was prepared from the Green Process of the near-critical water/CO₂, and the high value-added of the cellulose derivative was prudued in the newgreen solvent by one step using the obtained SBMC as raw material. In the meanwhile,the recycling of the ionic liquid solvent was achieved. The entire process was efficient,clean, and characteristic of entirely green transformation process from sugarcanebagasse cellulose to cellulose esters. The results were summarized as follows:Since the high concentration of H+were generated in near-critical water/CO₂under high temperature and high pressure, the sugarcane bagasse microcrystallinecellulose （SBMC） was prepared for the first time with SBC in near-critical water/CO₂,which overcomed the drawbacks of high-pollution and long-reaction time created bytraditional acid hydrolysis process. Based on a serial of experiments, the optimumsynthesis parameters, i.e., the reaction temperature is200℃the reaction time is60min, liquid-solid ratio is40:1, the initial reaction pressure is2MPa, had been obtained.The degree of polymerization （DP） of SBMC obtained under the above conditionswas215. During the SBC degradation process, the crystalline phases kept stable butthe breaking of glycosidic bonds was taken place. SBMC showed the short rod-likestructure and the uniform molecular weight distribution. The obtained SBMC had thefollowing parameters, i.e., the degree of crystallinity was74%,the initialdecomposition temperature was308.3°C, the content of the particle size above140mesh was87.2%, and the bulk density and shoot density were0.32g/cm3and0.46g/cm3, respectively.1-allyl-3-methylimidazolium chloride （AmimCl ionic liquid） was synthesizedwith Allyl chloride and N-methyl imidazole, and the dissolution and the influence oftemperature on the property of SBMC in AmimCl was studied. The results showedthat the initial decomposition temperature of AmimCl ionic liquids was270℃, the viscosity and density were1179mPa s and1.1438g/cm3respectively, and theobtained AmimCl had better thermal stability and flowability. Furthermore, theobtained SBMC could dissolve in AmimCl quickly and the homogeneous solutionwas formed at80℃for1h, This results were far superior to the cellulose, beingattribute to the lower polymerization degree and uniform molecular weight of SBMC.The three cellulose esters, cellulose acetate （CA, the degree of substitution from0.71to2.92）, cellulose acetate propionate （CAP, propionyl content from24.4to47.7%, acetyl content from1.7to10.3%）, cellulose acetate butyrate （CAB, butyrylcontent from27.5to52.8%acetyl content from1.7to9.7%）, had been made withhome-made SBMC in AmimCl. The substitution reactions occurred first in C6. Theinitial decomposition temperature of CA, CAP and CAB were353℃,346℃and341℃; respectively. The degree of crystallinity of CA, CAP and CAB were37.0%,47.5%and33.9%, respectively. The features viscosity of CA, CAP and CAB wereincreased with the molecular weight from1.00mL·g^-1,3.00mL·g^-1to5.00mL·g^-1respectively. CA, CAP and CAB had good solubility respectively in DMSO, acetone,butanone and so on.In order to better control of the reaction condition, get the esterization reactionbehavior of SBMC in AmimC, the homogeneous esterization kinetics of SBMC bothesterified with acetic anhydride and mixed anhydride （acetic anhydride and butyricanhydride） in AmimCl were studied. The reasearch found that the order of theesterization with acetic anhydride was1, and so was the esterization with aceticanhydride. The activation energy of the esterization with acetic anhydride was5.24kJ·mol^-1, the kinetic equation was Rg=3.15×10-2e^-17700/RT[MCC]1.0[Anhydl]0.04(mol·L^-1·s^-1). The activation energy of the esterization with mixed anhydride was9.64kJ·mol^-1, the kinetic equation was Rg=9.94×10^-2e^-20370/RT[MCC]^1.0[Anhydl]^0.039[Butyryl]^0.038(mol·L^-1·s^-1).Molecular distillation operating based on the differences in the mean free path ofgas molecules, had the characteristics of high seperation degree and lowtemperature,therefore, molecular distillation technology was used to recycle AmimClionic liquid after the acylate reaction of SBMC, and the reuse of the recycling ionicliquid（RIL） was also investigated. The results show that the optimum conditions ofthe recycled ionic liquid from esterization with acetic anhydride were as follows:distillation pressure was0.1Torr, distillation temperature was95℃, flow of thematerial was2mL/min, speed of the scraping film was413rpm. The optimumconditions of the recycled ionic liquid from esterization with mixed anhydride were asfollows: distillation pressure was0.1Torr, distillation temperature was110℃, flow ofthe material was2mL/min^-1, and speed of the scraping film was413rpm. The contentof the5th recycling-reusing ionic liquid was above99.5%. Compared with the fresh ionic liquid,5th recycling-reusing ionic liquid had the similar appearance andstructure. At the same time, the CA and CAB from the5th recycling-reusing ionicliquid also had the similar nature, such as the appearance, viscosity, degree ofsubstitution, structure etc.更多还原