Liquid–liquid equilibria measurements of ternary systems (acetonitrile + a carboxylic acid + dodecane) at 303.15 K

• The liquid–liquid equilibrium for (acetonitrile + acetic or propanoic or butanoic or 2-methylpropanoic or pentanoic or 3-methylbutanoic acid + dodecane) at 303.15 K were measured.
• Selectivity values for solvent separation efficiency were calculated from the tie-line data and show that separation of carboxylic acids from dodecane is feasible by extraction with acetonitrile.
• Three parameter equations have been fitted to the binodal curve data.
• The NRTL and UNIQUAC models were used to correlate the experimental data.

Liquid–liquid equilibrium (LLE) data are reported for the ternary mixtures of (acetonitrile + a carboxylic acid + dodecane) at 303.15 K under atmospheric pressure, where a carboxylic acid refers to acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid. The area of the two-phase heterogeneous region for the carboxylic acid mixtures decreases in the order: acetic acid > propanoic acid > butanoic acid > 2-methylbutanoic acid > pentanoic acid > 3-methylbutanoic acid. The relative mutual solubility of each of the carboxylic acids is higher in acetonitrile layer than in dodecane layer. Three 3-parameter equations have been fitted to the binodal curve data. The NRTL and UNIQUAC models were used to correlate the experimental data. The NRTL model fitted the experimental data far better than the UNIQUAC model with the average mean square deviation of 0.0030 mole fraction as compared to 0.2870 mole fraction for UNIQUAC. Selectivity values for solvent separation efficiency were calculated from the tie-line data and show that separation of carboxylic acids from dodecane is feasible by extraction with acetonitrile.