Selective extraction of cellulose from xylose residue using ionic liquids/DMSO: COSMO-RS prediction and experimental verification

Abstract

Efficiently dissolving and separating cellulose from xylose residue is beneficial to realize the high added-value of lignocellulosic waste. In this work, theoretical prediction by using COSMO-RS and practical experiments were combined to investigate the extraction selectivity of ionic liquids (ILs) for cellulose and lignin. Two imidazolium-based ILs, 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP) and 1-allyl-3-methylimidazolium chloride ([Amim]Cl), were screened out from 425 ILs. These ILs were subsequently mixed with dimethyl sulfoxide (DMSO) to dissolve and separate cellulose from xylose residue. The cellulose extraction efficiency of [Emim]DEP/DMSO were optimized by regulating the content of xylose residue, dissolution temperature and time. As the cellulose content was 1.2 wt%, the dissolution temperature of 80 °C, and the dissolving time of 120 min, the cellulose extraction rate of xylose residue could reach as high as 99.3% in [Emim]DEP/DMSO, which is higher than that in [Amim]Cl/DMSO (95.4%). The higher cellulose and lower lignin dissolution capacities of [Emim]DEP indicated that [Emim]DEP was a promising solvent to realize the conversion and utilization of cellulose in agro-industrial residues. In addition, [Emim]DEP presents constant dissolution capacity even it was recycled for five times. Furthermore, the produced xylose residue cellulose film (XRCF) displayed a homogeneous and smooth morphology with a tensile strength of 55.9 MPa, which had great potential in packaging.