作者:Shaokun Tang、Gary A. Baker、Sudhir Ravula、John E. Jones、Hua Zhao
DOI:10.1039/c2gc35631g
日期:——
Cellulose-dissolving ionic liquids (ILs) have become powerful neoteric solvents in the pretreatment of cellulosic biomass for ethanol fuel production. There are, however, a number of challenges to using current ionic solvents at large scales (imidazolium-based salts, in particular), including their relatively high costs and viscosities and their sluggish biodegradability. Aiming to overcome these hurdles, we have prepared a new series of poly(ethylene glycol) (PEG)-functionalized ILs comprising inexpensive alkylammonium or piperidinium cations paired with acetate anions. Some of these new ILs are capable of dissolving 8–12 wt% cellulose, while displaying low viscosities and acceptable thermal stabilities at the required process temperature. Our XRD and SEM data further confirm that regenerative pretreatment of cellulose by these PEGylated ILs can effectively transform the cellulose I structure to cellulose II, reducing the crystallinity of cellulose and increasing the structural homogeneity. Most excitingly, cellulose regenerated from these ILs can be rapidly hydrolyzed to glucose, in ∼90% glucose yield after 2 h, using a commercial cellulase supplemented with β-glucosidase.
纤维素溶解型离子液体(IL)已成为在生产乙醇燃料的纤维素生物质预处理过程中一种强有力的新型溶剂。然而,使用当前的离子溶剂(特别是咪唑盐类)在大规模应用时面临诸多挑战,包括成本和粘度较高、生物降解性不佳等问题。为了克服这些障碍,我们合成了一系列新型聚乙二醇(PEG)功能化的离子液体,这些离子液体采用廉价烷基铵或哌啶鎓阳离子与乙酸阴离子配对。其中一些新型离子液体能够溶解高达8-12 wt% 的纤维素,并且在所需的工艺温度下表现出低粘度和可接受的耐热性。通过XRD和SEM数据进一步证实,这些PEG化的离子液体对纤维素的再生预处理能够有效将纤维素I结构转变为纤维素II,从而降低纤维素的结晶度并增强结构均匀性。最令人兴奋的是,从这些离子液体中再生出的纤维素可以快速水解为葡萄糖,在添加了β-葡萄糖苷酶的商业纤维酶作用下,2小时后葡萄糖产率可达约90%。