Liquid–Liquid Equilibrium Measurement and Thermodynamic Modeling for Ternary Systems of 2-Ethyl-1-hexanol + 1,2-Propanediol + (Water and n-Heptane) at Different Temperatures

To recover 2-ethyl-1-hexanol and 1,2-propanediol from waste polyester alcoholysis products, liquid–liquid equilibrium (LLE) data for the ternary system of 2-ethyl-1-hexanol + 1,2-propanediol + (water, n-heptane) at different temperatures (303.2, 313.2, and 323.2 K) were studied at 101.3 kPa. The distribution coefficient (D) and selectivity coefficient (S) were used as indicators to assess the separation effect. The NRTL and UNIQUAC models were used to correlate the experimental data and the root mean square deviation (RMSD) values were calculated to be less than 0.75 and 0.97%, respectively. Finally, the consistency between the experimental data and the regression parameters was verified using the GUI-MATLAB tool. σ-Profiles are used to discuss the interactions of substances in this work. It was found that both extractants could separate and extract 2-ethyl-1-hexanol and 1,2-propanediol effectively, with water being more effective.