State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China.
State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China; Guangdong Engineering Research Center for Green Fine Chemicals, Guangzhou 510640, China.
Int J Biol Macromol. 2020 Jun 1;152:411-417. doi: 10.1016/j.ijbiomac.2020.02.241. Epub 2020 Feb 22.
Soda process is one of the most important pulping processes in paper industry producing large quantities of alkali lignins that can afford plenty of biofuels, aromatic chemicals and materials. However, the structural and size-related heterogeneities and complexities hinder the development in these directions. Herein, we report new insights into the structure of alkali lignin, through investigating the formation and transformation of enol ether and arylglycerol structures that are significant responsible for the structural transformation from native lignin to alkali lignin. Four-type enol ethers composed of G/S units in hardwood alkali lignin were identified by 2D HSQC NMR. A series of alkali lignins prepared by alkali treatment of eucalyptus cellulolytic enzyme lignin under various temperatures were analyzed by 2D HSQC NMR, P NMR and gel permeation chromatography (GPC). Upon these analyses and related model compound studies, it was found that the arylglycerols formed from native β-O-4 linkages tends to be oxidized with the further degradation of aryl ether bonds, and that the enol ether linkages are facile to be hydrolyzed or oxidized in the air. These insights improve the mechanistic understanding for the structural evolution and the diversity of alkali lignins and will aid the development of further lignin valorization strategies.
苏打法制浆是造纸工业中最重要的制浆工艺之一，可生产大量的碱木素，这些碱木素可提供丰富的生物燃料、芳香化学品和材料。然而，结构和尺寸相关的异质性和复杂性阻碍了这些方向的发展。在此，我们通过研究烯醇醚和芳基甘油结构的形成和转化，深入了解了碱木素的结构，这些结构对于从天然木质素到碱木质素的结构转化具有重要意义。通过二维 HSQC NMR 鉴定了来自硬木碱木质素的 G/S 单元组成的四种类型的烯醇醚。通过二维 HSQC NMR、P NMR 和凝胶渗透色谱（GPC）对在不同温度下用碱处理桉纤维素酶木质素制备的一系列碱木质素进行了分析。通过这些分析和相关模型化合物研究，发现来自天然β-O-4 键的芳基甘油容易与芳基醚键的进一步降解一起氧化，并且烯醇醚键在空气中易于水解或氧化。这些见解提高了对碱木质素结构演变和多样性的机制理解，并将有助于进一步开发木质素增值策略。
