深度共熔溶剂对尾叶桉木质素的溶解选择性

Solubility Selectivity for Lignin of Eucalyptus in Deep Eutectic Solvents

分别以三丁基甲基氯化铵（MTBAC）、四甲基氯化铵（TMAC）、苄基三乙基氯化铵（TEBA）和氯化胆碱（Ch Cl）为氢键受体与DL-乳酸（HL）以物质的量比为1∶9合成了深度共熔溶剂,考察了深度共熔溶剂的黏度及Hildebrand溶解度参数（δ）随温度的变化,并且将其应用于溶解桉木粉中的木质素。结果表明：由苄基三乙基氯化铵/DL-乳酸（TEBA/HL）合成的深度共熔溶剂溶解选择性最佳,用其处理40~60目的桉木粉,在90℃下反应10 h,木质素溶解率达92.3%,棕纤维素溶解率仅为8.3%,同时,木质素与棕纤维素溶解选择性系数之比（K值）为158.5,而MTBAC/HL、TMAC/HL及Ch Cl/HL的K值分别为113.8、16.8及49.7。FTIR测试结果表明：提取物中有木质素特征官能团。GPC测试结果表明：MTBAC/HL与TEBA/HL溶解分子量较大的木质素分子能力更强,MTBAC/HL和TEBA/HL分离产物的重均分子量分别是4 375和4 814,TMAC/HL和Ch Cl/HL分离产物重均分子量分别是3 674和3 977。CP/MAS13CNMR测试结果表明：90℃下TEBA/HL分离产物结构符合阔叶材木质素结构特征。

Four different kinds of deep eutectic solvents were synthesized with different quaternary ammonium salts and DL- lactic acid（ HL） in a 1∶9 mole ratio to dissolve lignin of eucalyptus. These salts composed of methyl tributyl ammonium chloride（ MTBAC）,tetramethylammonium chloride（ TMAC）,benzyl triethyl ammonium chloride（ TEBA） and choline chloride（ Ch Cl）. The changes of viscosity and Hildebrand solubility parameters（ δ） of the resulting solvents with temperature were investigated. It was found that deep eutectic solvents of TEBA / HL had the best solubility selectivity.When 40 ~ 60 mesh eucalyptus power was treated by TEBA / HL for 10 h under 90 ℃,the dissolution yield of lignin reached 92. 3% and the dissolution yield of total cellulose was only 8. 3%,meanwhile,the specific value（ K） of solubility selectivity coefficient between lignin and total cellulose reached158. 5. However,in the case of MTBAC / HL,TMAC / HL and Ch Cl / HL,their Ks were 113. 8,16. 8 and49. 7,respectively. FTIR spectrum analysis showed that extraction products contained lignin. And gel permeation chromatography（ GPC） analysis indicated that molecular weights of the products extracted by MTBAC / HL and TEBA / HL were 4 375 and 4 814,respectively,and higher than those of the products obtained by TMAC / HL（ 3 674） and Ch Cl / HL（ 3 977）,which indicated that MTBAC / HL and TEBA / HL had stronger ability to dissolve lignin with larger molecule weight. CP / MAS13 CNMR analysis suggested that structure characteristics of the extraction products by TEBA / HL at 90 ℃conformed to that of lignin of hardwoods.