纤维素在四己基醋酸铵/助溶剂混合体系中的溶解及再生

Dissolution and regeneration of cellulose in tetrahexylammonium acetate/co-solvent system

纤维素在自然界中储量丰富,是一种很好的生物质资源,但纤维素中含大量氢键,很难溶于常见有机溶剂,开发有效的纤维素溶解体系是纤维素应用的重点和难点。相对传统纤维素溶剂而言,离子液体具有对纤维素溶解性好,低毒性、难挥发等优点,成为近几年的研究热点。本研究通过离子交换法合成了四己基醋酸铵(THAA)离子液体,并分别以二甲基亚砜(DMSO)、N,N-二甲基乙酰胺(DMAc)和N,N-二甲基甲酰胺(DMF)为助溶剂对不同纤维素原料微晶纤维素、滤纸等进行溶解。探讨助溶剂类型、THAA含量、溶解温度和纤维素聚合度对THAA/助溶剂混合体系溶解纤维素的影响。结果表明,DMSO对纤维素溶解有促进作用,DMAc和DMF效果不大。当THAA/DMSO混合体系中THAA质量分数为30%时溶解纤维素性能最佳,25℃下能溶解7.51%的微晶纤维素。此外,纤维素在此溶剂体系中的溶解速度随溶解温度的升高及纤维素聚合度的降低而提高。纤维素经THAA/DMSO混合体系溶解再生后纤维素晶型由Ⅰ型变成Ⅱ型。

Cellulose is the most abundant renewable resource in nature. It is insoluble in most organic solvents due to the rich hydroxyl groups in ils structure which can form strong, three-dimensinnal inter- and irltra-mnlecular hydrogen bonding network. It is highly interest to develop effective cellulose dissolution system to broaden the applications of cellulnse. Ionic liquids （ILs） have received increasing attention due to their excellent dissolving abilities, low toxicity, and negligible vapeur pressure compared to traditional cellulose solvents. Tetrahexylammonium acetate （TH A A） was synthesized by ion exchange reaction. Dimethyl sulfoxide（DMSO） , dimethylacetamide（DMAc） and dimethyliormamide（DMF） were ehosen as the co-solvent for THAA used in cellulose dissolution. The effect uf en-solvent type, weight pen：entage of THAA in THAA/DMSO mixed solvent （w THAA） , dissolution temperature and the degree of polymerization （1）P） of the cellulose materials on the cellulose dissolutinn efficiency of the mixed solvent were studied. The results showed that DMSO was an excellent co-solvent for cellulose dissolution witb THAA while DMAc, DMF shewed poor abilities as the co-selvent for cellulose dissolution. The THAA/DMSO mixed solvent with w THAA = 30% possessed the highest cellulose solubility, in which 7.51% mieroerystalline cellulose can be （umpleted dissolved under 25 ℃. In addition, high dissululion temperature and low DP of cellulosic materials increased the dissolution rate of the process. Dissulved cellulose was regenerated by adding deionized water to the cellulose/THAA/DMSO solution. The XRD result showed that the regenerated eellulose ehanged from cellulose Ⅰ to cellulose Ⅱ.