Liquid–Liquid Equilibrium Investigations and Thermodynamic Modeling of Ternary Mixtures (Propylene Carbonate + Toluene or Phenol + <i>n</i>-Hexane or <i>n</i>-Octane) at 293.2 K

The liquid–liquid equilibria (LLE) of four ternary systems (propylene carbonate (PC) + toluene or phenol + n-hexane or n-octane) were studied at 293.2 K and 101.3 kPa. The study aimed to assess the effectiveness of PC in extracting nonpolar and polar aromatic compounds from alkanes with molar weights similar to gasoline components. Tie-line data and mutual solubilities were determined using refractive index measurements, while cloud point titration was employed to define binary phase regions. Systems with toluene exhibited Type I LLE behavior, while those with phenol showed Type II behavior. Experimental tie-lines were correlated with NRTL and UNIQUAC models, yielding rmsd values below 1%, indicating excellent model accuracy. NRTL binary interaction parameters were validated via MATLAB GUI tools, and activity coefficients were calculated. Toluene exhibited negative deviations from Raoult’s law in both phases, whereas phenol showed negative deviations at low phenol concentrations, with positive deviations observed in the alkane phase. Distribution coefficients and selectivities confirmed the strong extraction ability of PC, particularly for phenol, which exhibited values significantly higher than those of toluene, highlighting the greater separation efficiency for polar aromatic compounds.