Experimental and Thermodynamic Calculations on the Extraction and Separation of a 2,2,2-Trifluoroethanol + Water System Using Imidazole-Based Ionic Liquids

Abstract

Traditional methods prove challenging for separating 2,2,2-trifluoroethanol (TFE) from water due to the formation of an azeotrope. In order to be able to separate them effectively, five ILs were composed using three imidazolium ions ([EMIM]⁺, [BMIM]⁺, and [HMIM]⁺) as cations and bis(trifluoromethanesulfonyl)imide salt ([NTf₂]⁻) and hexafluorophosphate salt ([PF₆]⁻) as anions and were used as extractants for liquid–liquid extraction. And its liquid–liquid equilibrium (LLE) data of the ternary system of TFE + water + ILs were determined at 308.15 K and 101.325 kPa. The results showed that the selected ILs were able to achieve effective separation from a phase equilibrium point of view. Subsequently, the NRTL model was used to correlate the liquid–liquid equilibrium data obtained from the experiment to obtain the binary interaction parameters of the system. In addition, the σ-profiles of TFE, water, and related cations and anions of ILs were calculated, then the strength of the extraction ability for the adopted ILs was demonstrated by the interactions. The experimental results obtained can provide a basis for subsequent research on extracting fluoro alcohol and water azeotropes.