Liquid-Liquid Equilibrium for Extraction of 2,2-Difluoroethanol and Water with Ionic Liquids

2,2-Difluoroethanol (DFE) is an eco-friendly intermediate, which is employed to produce pharmaceuticals and fluoropolymers. During industrial manufacturing and practical use, an aqueous solution of DFE is usually generated. Owing to the formation of an azeotropic mixture of water and DFE, it is infeasible to separate such an azeotrope by conventional distillation due to its inherent thermodynamic limitations. Thus, extraction is considered for the separation of water and DFE. Three hydrophobic ionic liquids (ILs) {8-butyl-1,8-diazabicyclo [5,4,0]-7-undecene bis (trifluoromethyl sulfonyl) imide ([BDBU]NTf2), 1-butyl-1-methylmorpholinium bis (trifluoromethyl sulfonyl) imide ([BMMor]NTf2), and 1-butylpyridinium bis (trifluoromethyl sulfonyl) imide ([Bpy]NTf2)} were screened using the COSMO-SAC model for separating the azeotropic mixture. The liquid–liquid equilibrium data were ascertained for three mixtures (water + DFE + ILs). The computed data for partition ratio and selectivity of the extractants were employed for assessing their extraction capabilities. The NRTL equation was utilized to regress the obtained experimental data. The consistency of the fitting parameters was further verified. Finally, the intermolecular interactions between DFE/water and the ILs were analyzed and discussed from various perspectives by quantum chemistry calculations, providing a basis for designing rational IL structures to separate the azeotrope.