| 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. |
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