Fuente: Polymers Polymers, Vol. 18, Pages 1297: Synergistic Enhancement of Phenolic Hydroxyl Content in Lignin via Sequential Hydrothermal and Twin-Screw Extrusion Pretreatment Followed by Aqueous Ethanol Organosolv Extraction
Polymers doi: 10.3390/polym18111297
Authors:
Fangmin Liang
Ting Jiao
Jian Jiao
Chen Huang
Yan Lv
Yongjun Deng
Qingwen Tian
Ting Wu
Beiping Zhu
Shanming Han
Xuelian Zhou
Hongxiang Zhu
Guigan Fang
Fengshan Zhang
Yanshao Liu
Jingpeng Zhou

Lignin, the second most abundant polymer, remains largely underutilized, with nearly 90% of industrial lignin being combusted for energy due to its low phenolic hydroxyl content and structural heterogeneity of conventional extraction methods. The present study proposes a synergistic extraction method integrating sequential hydrothermal and twin-screw extrusion pretreatment followed by aqueous ethanol organosolv extraction. Three pretreatment strategies—hydrothermal pretreatment, twin-screw extrusion pretreatment, and sequential hydrothermal and twin-screw extrusion pretreatment—were compared. The sequential pretreatment exhibited the most favorable performance. Upon organosolv extraction, a lignin extraction rate of 67.9% was achieved, representing a 20.8% increase over that of the raw material. Extensive β-O-4′ bond cleavage during the integrated process liberated phenolic hydroxyl groups. This elevated the total phenolic hydroxyl content to 3.43 mmol·g−1, representing a 63.3% increase relative to lignin derived from raw material. Concurrently, this bond cleavage yielded lignin with a narrower molecular weight distribution, indicating enhanced structural homogeneity. Additionally, cellulose retention after lignin extraction reached 88.9%. Mass-balance calculations indicated that 1000 g of raw material yielded 82.5 g of xylose and xylooligosaccharides, 148.2 g of highly active lignin, and cellulose-enriched solid residues, thereby facilitating the comprehensive utilization of the three primary components of lignocellulosic biomass.