Exploring Protic and Aprotic Solvent Effects on the Molecular Properties of Furfurals in Ionic Liquids

Furfurals serve as a pivotal, suitable biomass-derived platform chemicals for producing assorted value-added chemicals, biofuels, and biochemicals. Ionic liquids (ILs) are used to form various furfurals from lignocellulosic biomass (LCB). However, different forms of furfurals interact differently with imidazolium-based ionic liquids (IMILs), making their separation from the ILs difficult. In this study, we perform molecular dynamics simulations to investigate the performance of different furfurals in the presence of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄], the protic solvent formic acid (FA), and the aprotic solvent hexamethylphosphoramide (HMPA). We consider seven different furfurals with distinct physiochemical properties, such as 2,5-bis(hydroxymethyl)furan (2BHF), 2,5-diformylfuran (2DFF), 2,5-dimethylfuran (2DMF), 2-methylfuran (2MF), furan-2,5-carboxylic acid (FCA), 2-furoic acid (FUA), and furan (FUR). We performed various structural, dynamic, and detailed thermodynamic analyses to understand their fundamental molecular behavior. In-depth atomic-level insights indicate that furfurals exhibit significant interaction with the solvent HMPA compared to FA. Based on the solvation free energy (ΔG_solv) and partition coefficient (log P) values, HMPA enhances the extraction ability of furfurals from the ILs. Overall, the results presented in this article provide guidance on furfural interaction behavior in the presence of protic and aprotic solvents for effective extraction.