Measurement and Correlation of the Liquid–Liquid Equilibrium for the Quaternary System N-Butanol + N-Pentanol + N-Hexanol + Water at 313.15, 323.15, and 333.15 K

For some strongly non-ideal solution systems, there are often errors in predicting the phase equilibrium relationship of a multi-component system using the interaction parameters obtained by the regression of the phase equilibrium data of the binary system. The interaction parameters between the components obtained by directly determining the phase equilibrium of the multivariate system will bring the calculated values closer to the experimental values. Liquid–liquid equilibrium (LLE) data were determined for the system of n-butanol + n-pentanol + n-hexanol + water at 313.15, 323.15, and 333.15K under atmospheric pressure. LLE compositions were determined by gas chromatography. LLE data were correlated by the UNIQUAC model and the non-random two-liquid (NRTL) model. Both models were appropriate for describing the LLE of this quaternary equilibrium system. They provided accurate thermodynamic parameters for the phase equilibrium of C4–6 mixed alcohols in Fischer–Tropsch synthesis water.