School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China; Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, Nanning, Guangxi 530006, China.
School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, Guangdong 510006, China.
Int J Biol Macromol. 2024 Apr;264(Pt 1):130475. doi: 10.1016/j.ijbiomac.2024.130475. Epub 2024 Feb 28.
Deep eutectic solvents (DES) are promising green solvents for depolymerization and reconstruction of lignin. Revealing the transformations of lignin during DES treatment is beneficial for high potential lignin applications. In this study, bagasse lignin was treated with a binary DES and three ternary DESs, respectively. The results showed that net hydrogen bonding acidity(α-β) value of DES was positively correlated to the increment of phenolic hydroxyl of lignin, and the ternary DES of choline chloride-formic acid-oxalic acid (ChCl-FA-OA) exhibited the best phenolation performances. The phenolic hydroxyl content of ChCl-FA-OA treated lignin was increased by 50.4 %, reaching 2.41 mmol/g under optimum conditions (120 °C, 4 h, ChCl-FA-OA = 1:2:1). Moreover, it was found that the cleavage of β-O-4' aryl ether bond and ester bond were dominant reactions during the treatment, accompanied by condensation reactions. Additionally, the obtained lignin oil contained various syringyl and guaiacyl derived phenolic compounds. Especially, the content of acetovanillone in lignin oil reached 29.94 %, much higher than in previous studies. Finally, the degradation mechanism of lignin in ChCl-FA-OA system was proposed. The present work provided insights into the relationship between lignin phenolation and DES properties. The novel ChCl-FA-OA system can achieve efficient lignin depolymerization, and convert lignin biomass into value-added chemical products.
深共熔溶剂（DES）是一种有前途的绿色溶剂，可用于木质素的解聚和重构。揭示木质素在 DES 处理过程中的转化有利于高潜力木质素的应用。在这项研究中，分别用二元 DES 和三种三元 DES 处理蔗渣木质素。结果表明，DES 的净氢键酸度（α-β）值与木质素酚羟基的增量呈正相关，而氯化胆碱-甲酸-草酸（ChCl-FA-OA）的三元 DES 表现出最好的酚化性能。在最佳条件（120°C，4 h，ChCl-FA-OA=1:2:1）下，ChCl-FA-OA 处理木质素的酚羟基含量增加了 50.4%，达到 2.41 mmol/g。此外，发现β-O-4'芳基醚键和酯键的断裂是主要反应，同时伴有缩合反应。此外，所得木质素油中含有各种愈创木基和紫丁香基衍生的酚类化合物。特别是，木质素油中乙酰香草酮的含量达到 29.94%，远高于以往的研究。最后，提出了 ChCl-FA-OA 体系中木质素的降解机制。本工作深入了解了木质素酚化与 DES 性质之间的关系。新型 ChCl-FA-OA 体系可实现高效木质素解聚，并将木质素生物质转化为高附加值的化学品。
