The low reactivity of lignin limits its performance in terms of selective oxidative cleavage of the C–C bond and most researchers employ lignin models as substrates for producing useful small molecules while the uses of real lignin are largely limited to low value material applications. Herein, a methanol/choline chloride (MeOH–ChCl)-based deep eutectic solvent (DES) was used to improve the solubility of lignin and the redox potential of the catalyst Cu(OAc)₂/1,10-phenanthroline. A high total yield of acetovanillone and acetic acid (87.12%) was obtained from alkaline lignin under mild conditions of 60 °C for 3 h. Two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectra indicated that condensation and depolymerisation reactions of side chain groups of alkaline lignin occurred simultaneously, and longer side chains may inhibit acetic acid formation, while more guaiacyl units may increase the acetovanillone yield. Additionally, this catalytic oxidation system has the potential to produce acetovanillone and acetic acid from DES extracted lignin, pretreated corncob and raw materials of corncob.

中文翻译：

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甲醇-氯化胆碱为基础的深共熔溶剂可增强木质素催化氧化为乙酰香草醛和乙酸的能力

木质素的低反应性限制了C-C键的选择性氧化裂解的性能，大多数研究人员采用木质素模型作为底物来生产有用的小分子，而真正的木质素的使用在很大程度上限于低价值的材料应用。在本文中，使用基于甲醇/氯化胆碱（MeOH–ChCl）的深共熔溶剂（DES）来改善木质素的溶解度和催化剂Cu（OAc）₂的氧化还原电势/ 1,10-菲咯啉。在60°C的温和条件下3小时，从碱性木质素中可得到高产率的乙酰香草醛和乙酸（87.12％）。二维异核单量子相干核磁共振（2D-HSQC NMR）光谱表明，碱性木质素侧链基团同时发生缩合和解聚反应，较长的侧链可能会抑制乙酸的形成，而更多的愈创木酰基单元可能会增加乙酰香草醛的产量。另外，该催化氧化系统具有从DES提取的木质素，预处理的玉米芯和玉米芯原料中生产乙酰香草醛和乙酸的潜力。