Liquid–liquid equilibria of (water + butyric acid + diethyl succinate or diethyl glutarate or diethyl adipate) ternary systems

Liquid–liquid equilibrium (LLE) data of the solubility (binodal) curves and tie-line end compositions were examined for mixtures of {(water (1) + butyric acid (2) + diethyl succinate or diethyl glutarate or diethyl adipate (3)} at 298.2 K and 101.3 ± 0.7 kPa. The relative mutual solubility of butyric acid is higher in the diethyl succinate or diethyl glutarate or diethyl adipate layers than water layers. The consistency of the experimental tie-lines was determined through the Othmer–Tobias correlation equation. The LLE data were correlated with NRTL model, indicating the reliability of the NRTL equations for these ternary systems. The best results were achieved with the NRTL equation, using non-randomness parameter (α = 0.3) for the correlation. Distribution coefficients and separation factors were measured to evaluate the extracting capability of the solvents.

Research highlights
► The relative mutual solubility of butyric acid is higher in the diethyl succinate or diethyl glutarate or diethyl adipate layers than water layers.
► The consistency of the experimental tie-lines was determined through the Othmer–Tobias correlation equation.
► The best results were achieved by NRTL model using non-randomness parameter (α = 0.3) for the correlation.