FeCl_(3)基三元低共熔溶剂分离毛竹木质素效率研究

Study on Lignin Fractionation Efficiency of Moso Bamboo by Ternary Deep Eutectic Solvents Based on FeCl_(3)

提高低共熔溶剂(DES)分离木质素效率是实现木质纤维资源高值化利用的前提。本研究基于酸性、中性及碱性二元DES分离毛竹木质素的方法,设计三元DES以提高木质素分离效率,优化三元DES分离木质素的工艺条件,采用Kamlet-Taft溶剂化显色参数,定量分析DES的氢键性能,并对DES分离所得木质素进行结构表征。结果表明,二元DES分离木质素时,木质素溶出率由高到低依次为:酸性DES>中性DES>碱性DES,由FeCl_(3)-聚乙二醇400-氯化胆碱构成的三元DES,其木质素溶出率较高,分离毛竹木质素的最佳工艺条件为:温度130℃、时间3 h、质量比1∶15、加水质量比10%(相对于聚乙二醇400质量);在此工艺条件下,木质素溶出率可达96.36%。FeCl_(3)的引入增加了三元DES的氢键碱性,使其具有更强的氢键接受能力。拉曼光谱和傅里叶变换红外光谱分析表明,DES分离所得毛竹木质素的主要基本结构单元为愈创木基型和紫丁香基型,且结构完整性优于碱木质素。本研究结果可为DES高效清洁分离毛竹木质素提供参考。

Improving the efficiency of lignin fractionation by deep eutectic solvents(DES)is an important prerequisite for the valorization of lignocellulosic resource.The acidic,neutral and alkaline binary DES systems were used for the lignin fractionation from moso bamboo.On this basis,a ternary DES system was designed to facilitate the lignin isolation rate.The process optimization of lignin fractionation using the ternary DES system,the quantitative analysis of hydrogen bond property via Kamlet-Taft method and the structural characterization of moso bamboo lignin isolated by DES were investigated,respectively.The results showed that the lignin dissolution rate of binary DES was in the order of acidic DES>neutral DES>alkaline DES,and the ternary DES system composed of FeCl_(3)-polyethylene glycol 400-choline chloride was more efficient in lignin dissolution with the optimum process conditions for the moso bamboo lignin fractionation with temperature at 130℃,time for 3 h,mass ratio of 1∶15 and water addition of 10%(proportion of polyethylene glycol 400).The dissolution rate was 96.13%under the optimum process conditions.The hydrogen bonding alkalinity of DES was increased significantly by coordinating FeCl_(3)in binary DES system,leading to a high hydrogen bond-accepting capacity.Both Raman and FT-IR spectroscopy analysis indicated that the main lignin basis structural units in DES lignin were S-type and G-type.Moreover,the structural integrity of DES lignin was better than that of alkali lignin.The results can provide a reference for the efficient and clean fractionation of moso bamboo lignin by DES.