Structural changes in lignins isolated using an acidic ionic liquid water mixture
Structural changes in lignins isolated using an acidic ionic liquid water mixture
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DOI：
10.1039/c5gc01314c
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发表时间：
2015-01-01
期刊：
影响因子：
9.8
通讯作者：
Hallett, Jason P.
中科院分区：
文献类型：
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作者：
Brandt, Agnieszka;Chen, Long;Hallett, Jason P.
近年来，基于硫酸氢阴离子的酸性离子液体水混合物被证明能有效地从木质纤维生物质中提取木质素。研究了用质子型离子液体1-丁基咪唑硫酸铵([HC(4)im][HSO4])提取，然后用反溶剂水沉淀分离出的芒属木质素。采用了定量C-13-核磁共振、H-1-C-13HSQC核磁共振、P-31-核磁共振、Py-GC-MS、GPC和元素分析等分析技术。分析表明，离子液体处理通过糖苷键、酯键和β-O-4醚键断裂木质素-半纤维素键，解聚木质素。这伴随着新生成的木质素碎片的增溶作用。在较长的预处理时间下，木质素碎片通过缩合反应发生再聚合。分离得到的木质素不含碳水化合物，硫含量低，相对分子质量低。早期木质素在结构上与球磨木素相似，而更多的处理木素富含对羟基苯基和愈创木基，并具有较高的酚羟基含量。我们的结论是，根据处理条件的不同，使用这种类型的离子液体溶液可以分离出具有各种特性的木质素。
Recently, acidic ionic liquid water mixtures based on the hydrogen sulfate anion have been shown to effectively extract lignin from lignocellulosic biomass. This study analyses Miscanthus giganteus lignin isolated after extraction with the protic ionic liquid 1-butylimidazolium hydrogen sulfate ([HC(4)im][HSO4]) followed by precipitation with the antisolvent water. Several analytical techniques were employed, such as quantitative C-13-NMR, H-1-C-13 HSQC NMR, P-31-NMR, Py-GC-MS, GPC and elemental analysis. The analysis shows that the ionic liquid pretreatment breaks lignin-hemicellulose linkages and depolymerizes the lignin through the cleavage of glycosidic, ester and beta-O-4 ether bonds. This is accompanied by solubilization of the newly generated lignin fragments. At longer pretreatment times, repolymerization of lignin fragments through condensation reactions occurs. The isolated lignins were carbohydrate-free, had low sulfur contents, low molecular weights. Early stage lignins were structurally similar to ball-milled lignin, while more treated lignins were enriched in p-hydroxyphenyl and guaiacyl units and had a high phenolic hydroxyl group content. We conclude that, depending on the treatment conditions, lignins with a variety of characteristics can be isolated using this type of ionic liquid solution.