Jiangsu Province Key Laboratory of Biomass Energy and Material; Jiangsu Province Co-Innovation Center of Efficient Processing and Utilization of Forest Resources; Key Lab. of Chemical Engineering of Forest Products, National Forestry and Grassland Administration; National Engineering Lab. for Biomass Chemical Utilization, Institute of Chemical Industry of Forestry Products, Chinese Academy of Forestry, Nanjing 210042, China.
Department of Biological Systems Engineering, University of Wisconsin-Madison, 460 Henry Mall, Madison, Wisconsin 53706, United States.
J Agric Food Chem. 2021 Nov 17;69(45):13568-13577. doi: 10.1021/acs.jafc.1c05759. Epub 2021 Nov 3.
To improve the reactivity and enrich the functionality of lignin for valorization, kraft lignin was depolymerized and demethylated via cleaving aryl and alkyl ether bonds in acidic lithium bromide trihydrate (∼60% LiBr aqueous solution). It was found that the cleavage of the ether bonds followed the order of β-O-4 ether > aryl alkyl ether in phenylcoumaran > dialkyl ether in resinol > methoxyl (MeO). The depolymerization via β-O-4 cleavage occurred under mild conditions (e.g., <0.5 M HCl at 110 °C), while sufficient demethylation of the lignin needed harsher conditions (>1.5 M HCl). Both depolymerization and demethylation generated new aromatic hydroxyl (ArOH). With 2.4 M HCl, MeO content dropped from 4.85 to 0.95 mmol/g lignin, and ArOH content increased from 2.78 to 5.09 mmol/g lignin. The depolymerized and demethylated kraft lignin showed excellent antioxidant activity and Cr(VI)-scavenging capacity, compared with original kraft lignin and tannins.
为了提高木质素的反应性并丰富其功能以实现其增值利用，通过在酸性溴化锂三水合物（约 60%的 LiBr 水溶液）中裂解芳基和烷基醚键，对 kraft 木质素进行了解聚和脱甲基。结果表明，醚键的裂解遵循β-O-4 醚＞苯并呋喃型二芳基醚＞树脂酚型二烷基醚＞甲氧基（MeO）的顺序。β-O-4 键的解聚是在温和的条件下发生的（例如，在 110°C 下 <0.5 M HCl），而木质素的充分脱甲基需要更苛刻的条件（>1.5 M HCl）。解聚和脱甲基都会产生新的芳基羟基（ArOH）。在 2.4 M HCl 下，MeO 含量从 4.85 mmol/g 木质素降至 0.95 mmol/g 木质素，而 ArOH 含量从 2.78 mmol/g 木质素增加至 5.09 mmol/g 木质素。与原 kraft 木质素和单宁相比，解聚和脱甲基的 kraft 木质素表现出优异的抗氧化活性和 Cr(VI)清除能力。
