Liquid–Liquid\nEquilibria for (Water + Propionic\nAcid or Butyric Acid + 2‑Octanol) at 298.2, 308.2, and 318.2\nK

Solubility and tie-line compositions were determined\nfor the aqueous\nmixtures of propionic and butyric acids with 2-octanol at <i>T</i> = (298.2, 308.2, and 318.2) K and 101 kPa. The ternary\nmixtures display type-1 liquid–liquid phase diagrams. To correlate\nthe experimental tie-line data, the thermodynamic models of NRTL and\nUNIQUAC were used. The calculated binary interaction parameters in\nthe NRTL model were reliable with the experimental liquid–liquid\nequilibrium (LLE) data through the model of Marcilla et al. The capacity\nof 2-octanol as a solvent was evaluated through the determination\nof solute distribution coefficient and selectivity. The effect of\ntemperature on the biphasic area was found to be small. The selected\nsolvent has a reasonably high extraction capacity and may serve as\na suitable separating agent for aqueous propionic or butyric acid\nmixtures. However, butyric acid is more hydrophobic in nature, exhibits\nlarger solute distribution coefficients and selectivities than propionic\nacid, and may be better extracted by the solvent.