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Protic, Aprotic, and Choline-Derived Ionic Liquids: Toward Enhancing the Accessibility of Hardwood and Softwood
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2019-09-11 , DOI: 10.1021/acssuschemeng.9b04443
Victoria Rigual 1 , Antonio Ovejero-Pérez 1 , Sandra Rivas 1 , Juan C. Domínguez 1 , M. Virginia Alonso 1 , Mercedes Oliet 1 , Francisco Rodriguez 1
Affiliation  

A side-by-side comparison of softwood (pine) vs hardwood (eucalyptus) pretreatment using 3 protic, 3 aprotic, and 3 choline-derived ionic liquids (ILs) is proposed. While the protic ionic liquid 2-hydroxyethylammonium formate leads to alkali lignin dissolution at 30 °C after 1 h, the lack of interactions with the whole-cell wall limits the biomass disruption. On the contrary, the protic ionic liquid 1-methylimidazolium chloride produces a catalytic effect that extracts almost all of the hemicelluloses, and partially the lignin. Remarkable digestibilities are obtained with choline acetate ([Ch][OAc]) in eucalyptus (69%), while in pine, protic, and choline-derived ILs tested do not appear to be real “greener” alternatives to conventional ILs such as 1-ethyl-3-methylimidazolium acetate (the highest digestibility, 84%). Solid morphology revealed a smoother surface in pine pretreated with [Mim][Cl], and confocal fluorescence microscopy was used to distinguish surface holocellulose and lignin, highlighting differences in the accessibility of hardwood vs softwood due to the presence of surface lignin. Two-dimensional nuclear magnetic resonance spectroscopy of saccharified samples pretreated with [Ch][OAc] showed the presence of groups derived from acetate. Finally, thermogravimetric analysis and spectroscopy techniques reveal the difficulties in recovering the ionic liquid and conclude a work that describes the strengths and weaknesses of the ILs and biomasses studied.

中文翻译:

质子,无质子和胆碱衍生的离子液体:旨在提高硬木和软木的可及性

提出了使用3种质子,3种非质子和3种胆碱衍生的离子液体(IL)进行的软木(松木)与硬木(桉树)预处理的并排比较。质子离子液体甲酸2-羟乙基铵导致1小时后在30°C时碱木质素溶解,但与全细胞壁相互作用的缺乏限制了生物质的破坏。相反,质子离子液体1-甲基咪唑氯化物产生催化作用,该作用几乎提取了所有的半纤维素,并且部分地提取了木质素。乙酸胆碱([Ch] [OAc])在桉树(69%)中获得了显着的消化率,而在松树,质子和胆碱衍生的IL中,似乎不是传统ILs的真正“绿色”替代品,例如1 -乙基-3-甲基咪唑乙酸盐(最高消化率,84%)。固体形态显示,经[Mim] [Cl]预处理的松树表面较光滑,共聚焦荧光显微镜用于区分表面全纤维素和木质素,突出显示了由于存在表面木质素,硬木与软木可及性的差异。用[Ch] [OAc]预处理的糖化样品的二维核磁共振波谱表明存在衍生自乙酸盐的基团。最后,热重分析和光谱技术揭示了回收离子液体的困难,并完成了描述所研究的离子液体和生物质的优缺点的工作。强调由于表面木质素的存在,硬木与软木在可及性上的差异。用[Ch] [OAc]预处理的糖化样品的二维核磁共振波谱显示存在衍生自乙酸盐的基团。最后,热重分析和光谱技术揭示了回收离子液体的困难,并完成了描述所研究的离子液体和生物质的优缺点的工作。强调由于表面木质素的存在,硬木与软木在可及性上的差异。用[Ch] [OAc]预处理的糖化样品的二维核磁共振波谱表明存在衍生自乙酸盐的基团。最后,热重分析和光谱技术揭示了回收离子液体的困难,并完成了描述所研究的离子液体和生物质的优缺点的工作。
更新日期:2019-09-11
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