Atmospheric one-pot fractionation and catalytic conversion of lignocellulose in multifunctional deep eutectic solvent system

This study developed a “one-pot” three-stage process using a “multifunctional” deep eutectic solvent (DES) containing choline chloride (ChCl), ethylene glycol (EG), and protonic acids for the production of phenolic monomers, furfural, and glucose. In the first stage, the DES effectively dissolved over 70 % of lignin and 78 % of hemicellulose while preserving aryl ether bonds in lignin due to the grafting of EG onto the aryl ether bonds. Concurrently, the retention of a near-quantitative amount of cellulose led to a glucose yield of >80 % after enzymatic saccharification. In the next stage, the DES enabled the catalytic depolymerization of lignin using a Ru/C catalyst at mild temperatures and atmospheric pressure, eliminating the need for an external hydrogen source and yielding G/S-propyl and G/S-propenyl monomers at 13.8 %. Additionally, the ratio of ChCl to EG in the DES could regulate the composition and selectivity of the phenolic monomers. Following this, the hemicellulose sugars dissolved in the DES underwent catalytic hydrolysis in a DES/water system, achieving a furfural yield of 36.4 % under optimized conditions. The results of this study offer important insights into the valorization of lignocellulose in “one-pot” under mild conditions, thereby advancing the field of biorefining.