Elucidating the structural characteristics and changes of lignin during biorefining is considerably significant for lignin valorization. Deep eutectic solvent (DES), as a green solvent, has shown excellent performance in extracting high-purity lignin from lignocellulose with high yields. However, further utilization of the multiple novels DES remains to be a severe challenge to the biorefinery process. In this study, alkaline lignin (AL), which was separated from sugarcane (Sacharum officinale L.) bagasse (SCB), was pretreated by a ternary DES (TDES) (choline chloride (ChCl)-lactic acid (LA)/oxalic acid (OA)-AlCl₃·6H₂O) at 120 °C for 6 h to obtain regenerated lignin. The properties and structural transformation of lignin during the TDES pretreatment were investigated by gel-permeation chromatography (GPC), two-dimensional-heteronuclear single quantum correlation nuclear magnetic resonance (2D-HSQC NMR), ³¹P NMR, Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). Finally, the degradation products recovered from TDES pretreatment were also analyzed by pyrolytic gas chromatography-mass spectrometry (Py-GC–MS). It was found out that the yields of the regenerated lignin pretreated by ChCl-LA-AlCl₃·6H₂O and ChCl-OA-AlCl₃·6H₂O were 65.40 and 55.43 %, respectively. In contrast, the contents of phenolic hydroxyl groups in lignin were 2.54 and 2.84 mmol g⁻¹, respectively, the content of aliphatic hydroxyl groups were 0.91 and 0.79 mmol g⁻¹, respectively. In addition, it is found that the depolymerization of the lignin fraction was the dominant reaction during the TDES pretreatment. Based on the observed results, a possible pathway of chemical conversion of SCB lignin during the TDES pretreatment process was proposed. This study shows that the pretreatment with hydrated metal chloride-based TDES provides a promising condition for generating of the value-added lignin in the current biorefinery process.

阐明生物精炼过程中木质素的结构特征和变化对于木质素的价值化具有重要意义。深共熔溶剂（DES）作为一种绿色溶剂，在以高产率从木质纤维素中提取高纯度木质素方面表现出优异的性能。然而，进一步利用多种新型 DES 仍然是生物炼制过程的严峻挑战。在这项研究中，从甘蔗 ( Sacharum officinale L. ) 甘蔗渣 (SCB)中分离出来的碱性木质素 (AL)用三元 DES (TDES)（氯化胆碱 (ChCl)-乳酸 (LA)/草酸(OA)-AlCl ₃ ·6H ₂O) 在 120°C 下 6 小时以获得再生木质素。通过凝胶渗透色谱（GPC）、二维异核单量子相关核磁共振（2D-HSQC NMR）、³¹ P NMR、傅里叶变换红外光谱（FT -IR) 和热重分析 (TGA)。最后，还通过热解气相色谱-质谱（Py-GC-MS）分析了从 TDES 预处理中回收的降解产物。发现ChCl-LA-AlCl ₃ ·6H ₂ O和ChCl-OA-AlCl ₃ ·6H ₂预处理再生木质素的产率O分别为65.40%和55.43%。相比之下，木质素中酚羟基的含量分别为2.54和2.84 mmol g ^-1，脂肪族羟基的含量分别为0.91和0.79 mmol g ^-1。此外，发现木质素部分的解聚是 TDES 预处理过程中的主要反应。根据观察结果，提出了 TDES 预处理过程中 SCB 木质素化学转化的可能途径。该研究表明，水合金属氯化物基 TDES 的预处理为在当前的生物精炼工艺中产生增值木质素提供了有希望的条件。