Effect of Choline-Based Deep Eutectic Solvent Pretreatment on the Structure of Cellulose and Lignin in Bagasse

Cuicui Li,Chaojian Zheng,Yuan Zhao,Wanru Luo,Chongxing Huang,Shuangfei Wang,Lanyu Zhang,Hui Zhao,Hongxia Su,Li-Jie Huang

doi:10.3390/pr9020384

Abstract

Deep eutectic solvents (DESs) is a newly developed green solvent with low cost, easy preparation and regeneration. Because of its excellent solubility and swelling effect in lignocellulose, it has received widespread attention and recognition. In this study, choline-based deep eutectic solvents (DESs)—choline chloride-urea (CC-U), choline chloride-ethylene glycol (CC-EG), choline chloride-glycerol (CC-G), choline chloride-lactic acid (CC-LA), and choline chloride-oxalic acid (CC-OA)—were used to extract and separate bagasse. The effects of hydrogen bond donors on lignin separation and the fiber and lignin structure were investigated. All five DESs could dissolve lignin from bagasse; acidic DESs exhibited higher solubility than basic DESs. CC-OA effectively separated lignin and hemicellulose. CC-LA showed weaker lignin separation ability than CC-OA. CC-G, CC-EG, and CC-U were more inclined to selectively separate lignin than hemicellulose. The crystalline cellulose II structure was retained after DES pretreatment. Acidic DESs effectively improved the crystallinity of bagasse fiber; the crystallinities for CC-OA and CC-LA pretreatment were 62.26% and 61.65%, respectively. The lignin dissolved in DES was mainly syringyl lignin. The lignin dissolved in CC-U, CC-LA, and CC-OA contained a small amount of guaiacyl lignin.

Highlights

As a substitute for petrochemical resources, renewable resources have become an important raw material for the green and sustainable development of industries
Lignocellulose resources, which are rich in cellulose, hemicellulose, and lignin, are the most widely distributed and abundant renewable resources on earth [1]
Bagasse was used as the raw lignocellulosic material, its composition is shown in Table

Summary

Introduction

As a substitute for petrochemical resources, renewable resources have become an important raw material for the green and sustainable development of industries. Lignocellulose resources, which are rich in cellulose, hemicellulose, and lignin, are the most widely distributed and abundant renewable resources on earth [1]. A cellulose residue obtained after crushing and pressing sugarcane juice, is an important renewable biomass resource. Bagasse is considered an ideal fiber material. Bagasse is mainly composed of cellulose, hemicellulose, and lignin, of which cellulose accounts for approximately 46–55% [3]. The rapid and effective removal of hemicellulose and lignin while maintaining the structure and form of cellulose has been a challenge in the use of bagasse

Methods

Results

Conclusion