Liquid–liquid phase equilibrium in ternary mixture of waste fish oil biodiesel–methanol–glycerol: Experimental data and thermodynamic modeling

Liquid–liquid Equilibrium (LLE) of waste fish oil biodiesel, methanol and glycerol were studied at three temperatures (298.15, 313.15, and 328.15 K). The experimental measurements were carried out at fixed temperatures at atmospheric pressure. The experimental data were correlated by NRTL and UNIQUAC activity coefficient models. Predictive models such as UNIFAC, UNIFAC-LLE, UNIFAC-LBY, UNIFAC-DMD and NIST-modified UNIFAC were used to obtain the equilibrium compositions. All models could well predict the experimental data. Deviations between the calculated and experimental data for NRTL, UNIQUAC, UNIFAC, UNIFAC-LLE, UNIFAC-LBY, UNIFAC-DMD, and NIST-modified UNIFAC were 2.05%, 2.85%, 2.09%, 2.60%, 3.30%, 2.04%, and 2.05% respectively which show that UNIFAC-DMD model could better correlate the experimental data.