Experimental and mechanistic study on liquid-liquid equilibrium for the separation of cyclohexane and ethyl acetate using imidazolium ionic liquids

Cyclohexane and ethyl acetate, as essential organic solvents, are hard to separate effectively because they form an azeotropic mixture. Due to the limitations of traditional methods, developing eco-friendly separation technologies is crucial. In this work, COSMOthermX was used to screen two ionic liquids (ILs) 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][NTF2]) and 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl)imide ([BMIM][NTF2]) as extractants for the separation of ethyl acetate and cyclohexane. The liquid-liquid equilibrium (LLE) data of cyclohexane + ethyl acetate + [EMIM][NTF2]/[BMIM] [NTF2] were measured at 298.15, 308.15, and 318.15 K. Furthermore, the reliability of the experimental data was evaluated using the Othmer-Tobias equation. The nonrandom two-liquid (NRTL) model was employed to correlate the LLE data and derive the corresponding model parameters. The fact that the root-mean-square deviation (RMSD) value is less than 1.5 %, indicates good correlation between the NRTL model and the experimental data. Based on macroscopic experimental findings, when xethyl acetate = 0.0657 in the initial system, the S[EMIM][NTF2] and S[BMIM][NTF2] are 47.97 and 32.64, respectively. Under these conditions, molecular dynamics (MD) simulations were utilized to investigate the microscopic mechanism of LLE. By analyzing the self- diffusion coefficients (D) and radial distribution function (RDF), it can be concluded that the extraction performance of [EMIM][NTF2] is greater than that of [BMIM][NTF2]. Through experimental results and microscopic mechanism analysis, ILs have been proven to efficiently extract ethyl acetate from mixture. In addition, an efficient extraction process was designed based on the selected IL using Aspen Plus.