Joint BioEnergy Institute, Emeryville, California 94608, USA.
J Phys Chem B. 2012 Aug 23;116(33):10049-54. doi: 10.1021/jp304538v. Epub 2012 Aug 10.
Ionic liquids (ILs) have been shown to affect cellulose crystalline structure in lignocellulosic biomass during pretreatment. A systematic investigation of the swelling and dissolution processes associated with IL pretreatment is needed to better understand cellulose structural transformation. In this work, 3-20 wt % microcrystalline cellulose (Avicel) solutions were treated with 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]) and a mixture of [C(2)mim][OAc] with the nonsolvent dimethyl sulfoxide (DMSO) at different temperatures. The dissolution process was slowed by decreasing the temperature and increasing cellulose loading, and was further retarded by addition of DMSO, enabling in-depth examination of the intermediate stages of dissolution. Results show that the cellulose I lattice expands and distorts prior to full dissolution in [C(2)mim][OAc] and that upon precipitation the former structure leads to a less ordered intermediate structure, whereas fully dissolved cellulose leads to a mixture of cellulose II and amorphous cellulose. Enzymatic hydrolysis was more rapid for the intermediate structure (crystallinity = 0.34) than for cellulose II (crystallinity = 0.54).
离子液体（ILs）已被证明会在预处理过程中影响木质纤维素生物质中的纤维素结晶结构。需要对与 IL 预处理相关的溶胀和溶解过程进行系统研究，以便更好地理解纤维素的结构转化。在这项工作中，用 1-乙基-3-甲基咪唑醋酸盐([C(2)mim][OAc])和[C(2)mim][OAc]与非溶剂二甲基亚砜(DMSO)的混合物处理了 3-20wt%的微晶纤维素（Avicel）溶液，处理温度不同。随着温度的降低和纤维素负载量的增加，溶解过程减缓，添加 DMSO 进一步减缓，从而能够深入研究溶解的中间阶段。结果表明，纤维素 I 晶格在完全溶解于 [C(2)mim][OAc]之前先膨胀和变形，而在沉淀时，前者的结构导致形成一种较无序的中间结构，而完全溶解的纤维素则形成纤维素 II 和无定形纤维素的混合物。对于中间结构（结晶度=0.34），酶水解比纤维素 II（结晶度=0.54）更快。
