Liquid–liquid equilibria for ternary systems polyoxymethylene dimethyl ethers + para-xylene + water

• The LLE for ternary systems (PODEn + PX + H2O) was measured at T = 293.15 K, 313.15 K.
• PX were studied as an effective solvent to extract PODEn from aqueous solution.
• The NRTL and UNIQUAC models were used to correlate the experimental data.
• The consistency of the LLE data were tested by Hand correlations and Othmer–Tobias.

Polyoxymethylene dimethyl ethers (PODEn) are promising diesel additives which can be synthesized from formaldehyde and methanol. In this work, the ternary liquid–liquid equilibria (LLE) were analytically determined at 293.15 K and 313.15 K for the following systems: PODE1 + para-xylene (PX) + water, PODE2 + PX + water, PODE3 + PX + water, PODE4 + PX + water, respectively. The isothermal experimental results have shown a good linear fit in Hand plots and the Othmer–Tobias. The design of the solvent extraction equipment for extracting PODEn from aqueous solution requires an appropriate model for the liquid–liquid phase equilibrium. The well-known NRTL and UNIQUAC thermodynamic models were applied to correlate the experimental data, and the results indicate that the UNIQUAC model gives a better agreement.