N-Ethyl-N-methylpyrrolidine Thiocyanate: Thermodynamic Parameters Measurements and Application Potential in Separation of the Azeotrope

This study investigated the thermodynamic parameters of ionic liquid N-ethyl-N-methylpyrrolidine thiocyanate ([EMPYR][SCN]) by using inverse gas chromatography. The parameters included weight fraction activity coefficients (Ω₁₂^∞), Flory–Huggins interaction parameters (χ₁₂^∞), and infinite dilution activity coefficients (γ₁₂^∞). Based on these, the vapor–liquid equilibrium data of the [EMPYR][SCN]-solvent system at 343.15 K were determined, and the key nonrandom two liquid model parameters were obtained through fitting. The Aspen Plus software was utilized to draw the equilibrium phase diagram of the ternary system ([EMPYR][SCN]-methanol/ethanol/thiophene-benzene), which confirmed its effectiveness in separating three azeotropic mixtures. Comparative analysis indicated that compared with four other ILs, [EMPYR][SCN] exhibited better separation performance in the benzene/thiophene system, highlighting its potential as an efficient solvent for azeotrope separation.