Comparison of lignin and cellulose solubilities in ionic liquids by COSMO-RS analysis and experimental validation

In this work, the solubilities of lignin and cellulose in ionic liquids (ILs) have been analyzed and compared by COSMO-RS simulation. The excess enthalpy of the IL + lignin/cellulose mixtures is evaluated as reference property to describe the affinity of lignin and cellulose for different ionic liquids, in terms of the intermolecular interactions contributing to their mixing properties. Thus, the anion plays the main role in the dissolution process of both lignin and cellulose, in which the hydrogen bonding forces are the major interactions. The most promising anions for the cellulose and lignin dissolution are acetate, formate and chloride, whereas different cations can be employed. Computational results indicated that a rational combination of the anions and cations allows designing ILs able to dissolve with different selectivity lignin and cellulose. Some of these solutions are tested in the laboratory to validate the model employed and the regenerated solids are analyzed by FTIR spectroscopy.

► Simulation of lignin and cellulose solubilities in ionic liquids by COSMO-RS.
► COSMO-RS results were experimentally validated for a selected set of ionic liquids.
► Excess enthalpy predicts lignin and cellulose solubilities in ionic liquids.
► The hydrogen bonding is the main interaction in lignin and cellulose dissolution.
► COSMO-RS allows selecting ionic liquids for cellulose and lignin dissolution.