Valorization of Lignin to Simple Phenolic Compounds over Tungsten Carbide: Impact of Lignin Structure

详细信息    查看全文

• 作者：Haiwei Guo ; Dr. Bo Zhang ; Zaojuan Qi ; Dr. Changzhi Li ; Jianwei Ji ; Tao Dai ; Prof. Aiqin Wang and Prof. Tao Zhang
• 刊名：ChemSusChem
• 出版年：2017
• 出版时间：February 8, 2017
• 年：2017
• 卷：10
• 期：3
• 页码：523-532
• 全文大小：1410K
• ISSN：1864-564X

文摘

Lignins isolated from representative hardwood, softwood, and grass materials were effectively hydrocracked to aromatics catalyzed by tungsten carbide over activated carbon (W₂C/AC). The effects of botanical species and fractionation methods on lignin structure and the activity of W₂C/AC were studied in detail. Gas permeation chromatography (GPC), FTIR, elemental analysis, and 2 D HSQC NMR showed that all the extracted samples shared the basic skeleton of lignin, whereas the fractionation method significantly affected the structure. The organosolv process provided lignin with a structure more similar to the native lignin, which was labile to be depolymerized by W₂C/AC. Softwood lignins (i.e., spruce and pine) possessed higher molecular weights than hardwood lignins (i.e., poplar and basswood); whereas corn stalk lignin that has noncanonical subunits and exhibited the lowest molecular weight owing to its shorter growth period. β-O-4 bonds were the major linkages in all lignin samples, whereas softwood lignins contained more resistant linkages of β-5 and less β-β than corn stalk and hardwood lignins; as a result, lowest hydrocracking efficiency was obtained in softwood lignins, followed by corn stalk and hardwood lignins. 2 D HSQC NMR spectra of lignin and the liquid oil as well as the solid residue showed that W₂C/AC exhibited high activity not only in β-O-4 cleavage, but also in deconstruction of other ether linkages between aromatic units, so that high yield of liquid oil was obtained from lignin.