Integrated strategies for furfural production and lignocellulose fractionation in aqueous deep eutectic solvents

Abstract

The current biomass refinery pretreatment using deep eutectic solvents (DES) has primarily focused on downstream utilization of cellulose and lignin, while often overlooking the potential of hemicellulose. Herein, an innovative and integrated strategy was proposed for simultaneous production of furfural (FF) and fractionation of lignin and cellulose from biomass using the same aqueous DES. To achieve this goal, response surface methodology (RSM) was employ to optimize the dilute hydrochloric acid (HA) pretreatment of corn stover, a representative of lignocellulosic material, ensuring complete removal of hemicellulose. The resulting hemicellulose hydrolysate was then efficiently converted into FF in aqueous DES system, achieving an impressive yield of 72.82 %. By introducing MgCl2 as a catalyst, the FF yield soared to an exceptional 86.94 %. Furthermore, a plausible mechanism was elucidated for the conversion of hemicellulose to FF in the aqueous DES. Concurrently, the solid residue resulting from the dilute HA pretreatment was fractionated using the same aqueous DES, successfully extracting cellulose and lignin fractions. Notably, the separated cellulose solid residue exhibited an outstanding digestion efficiency of 96.3 % after 72 h of enzymatic hydrolysis at 30 FPU/g, as confirmed through meticulous FTIR analyses. In addition, an advanced 2D-HSQC NMR technique was utilized to unveil the intricate structure of the obtained lignin, revealing a guaiacol-syringyl-p-hydroxyphenyl (G-S-H) type lignin enriched with abundant CH3O- and β-O-4 linkages. A mass balance analysis showed the production of 14.0 g FF, 31.9 g glucose and 14.2 g lignin from 100 g dry corn stover. This state-of-the-art approach presented not only pioneers a novel avenue for the concurrent production of FF but also offers a sustainable and eco-friendly method for the fractionation of lignin and cellulose using DES solvents.