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.