Ionic liquid screening for lignocellulosic biomass fractionation: COSMO–RS prediction and experimental verification

The fractionation of lignocellulosic biomass is vital for advancing its applications, particularly in the extraction of high-demand cellulose. In this study, 378 ionic liquids (ILs), comprising of 18 anions and 21 cations, were selected to predict lignocellulosic biomass fractionation using COSMO–RS. The selectivity of the cellulose model to the lignin model in the prediction indicates that the dissolution and separation of lignocellulosic biomass are primarily governed by the anion, and the carboxylate and amino acid anions present the most effective separation effect among the ILs. Moreover, the pretreatment and composition analysis of cornstalk using five representative ILs indicated consistency with the predicted selectivity. The higher calculated excess enthalpy between cellulose and the IL, compared to that between lignin and the IL, led to increased cellulose dissolution by the IL, ultimately resulting in the separation of lignocellulose. This study provides a new paradigm for directly predicting the selectivity of IL to cellulose and lignin and designing ILs capable of achieving lignocellulosic biomass fractionation through COSMO–RS simulation.