Liquid-liquid phase equilibrium measurement and thermodynamic modeling for the separation of n-hexane and methanol with four solvents

To solve the problem of generating n-hexane in the industrial production of methanol, four common and inexpensive solvents {dimethyl sulfoxide, 1,2-propanediol, furfuryl alcohol, and furfural} were chosen as extractants to separate n-hexane and methanol. The liquid–liquid equilibrium (LLE) data of n-hexane + methanol +{dimethyl sulfoxide, 1,2-propanediol, furfuryl alcohol, or furfural} were measured at 303.2 K and 101.3 kPa. The extraction performance of four extractants was evaluated by the distribution coefficient ( D ) and separation factor ( S ). At the same time, NRTL and UNIQUAC models were used to fit the experimental LLE data to obtain regression parameters. The reliability of the binary interaction parameters was verified by the mixed surface analysis based on Gibbs energy topology. The root mean square deviation ( RMSD ) of the NRTL and UNIQUAC models are less than 0.0040 and 0.0057, respectively, indicating that the NRTL and UNIQUAC models are suitable for the study of this system. Furthermore, the interaction energy between extractant and methanol molecules was analyzed by the DMol3 module and the effect difference of liquid–liquid extraction was explained from the perspective of interaction energy using σ-Profile.