Deep eutectic solvents (DESs) composed by carboxylic acids and quaternary ammonium salts are potential candidate for lignocellulose dissolution and pretreatment. To both explore the most efficient DESs for lignocellulose dissolution and pretreatment as well as unveil the process mechanism, DESs composed by carboxylic acids as the hydrogen bond donors (HBDs) and quaternary ammonium salts as the hydrogen bond acceptors (HBAs) were prepared and further applied for kraft lignin (KL) dissolution as well as poplar and pine pretreatment. We found DES composed by lactic acid (LA) and allyltrimethylammonium chloride (ATMAC) with mole ratio of 2:1 is high-efficient for the dissolution of KL. In addition, 70% poplar lignin and 82% pine lignin could be removed at 120 ℃ for 6 h with a solid-to-liquid ratio of 1:10. Furthermore, the -OH and -COOH groups in HBDs of DESs provided active protons to cleave ether bonds and part of carbon-carbon bonds during lignin dissolution and extraction. Additionally, the KL solubility and the Kamlet-Taft (K-T) parameters (α and π * ) of the DESs showed good positive correlation. These findings give a deep insight into the dissolution mechanism of KL and pretreatment of lignocellulose, which is helpful for designing robust DESs for dissolution and pretreatment of lignocellulose.

由羧酸和季铵盐组成的低共熔溶剂 (DES) 是木质纤维素的潜在候选者溶解和预处理。为了探索最有效的木质纤维素溶解和预处理 DES 并揭示其工艺机理，制备并进一步应用了由羧酸作为氢键供体 (HBD) 和季铵盐作为氢键受体 (HBA) 组成的 DES。用于牛皮纸木质素 (KL) 的溶解以及杨树和松树的预处理。我们发现由乳酸（LA）和烯丙基三甲基氯化铵（ATMAC）组成的DES，摩尔比为2：1，对KL的溶解效率很高。此外，70%的杨木木质素和82%的松木木质素可以在120 ℃下6 h去除，固液比为1:10。此外，HBD 中的 -OH 和 -COOH 基团的 DES 提供了活性质子来在木质素溶解和提取过程中裂解醚键和部分碳-碳键。此外，DESs 的 KL 溶解度和 Kamlet-Taft (KT) 参数（α 和 π * ）显示出良好的正相关性。这些发现深入了解了 KL 的溶解机制和木质纤维素的预处理，这有助于设计稳健的 DES 用于木质纤维素的溶解和预处理。