High-Pressure Vapor-Liquid Equilibrium Computations Using the Hayden-O'Connell Method and Wilson Model

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Consider a binary mixture of -butanol and -butyl acetate. This Demonstration computes vapor-liquid equilibrium data for this mixture at various pressures. We use the Wilson model for the prediction of liquid-phase activity coefficients and the Hayden–O'Connell method to compute the gas-phase fugacity coefficients.


This binary mixture presents a peculiar behavior: indeed, the azeotrope, which is present at low pressure ( -butanol at ), disappears at high pressures (e.g. at ).

The Demonstration plots gas-phase fugacity coefficients for user-specified values of the pressure (expressed in psi).

A comparison with the results obtained using ASPEN (http://www.aspentech.com/) for is also shown for both the equilibrium curve and the -value for -butanol (cyan dots come from ASPEN).

In order to use the Hayden–O'Connell method, which takes into account deviations from ideal gas-phase behavior at moderate and high pressures, one has to compute second-order virial coefficients , , and or ) versus temperature. The Demonstration computes and plots these latter coefficients and compares the results obtained in the present study with the data (red dots) calculated by a Fortran program kindly provided by Professor J. P. O'Connell.


Contributed by: Housam Binous and Eid Al-Mutairi (March 2011)
Open content licensed under CC BY-NC-SA




[1] J. G. Hayden and J. P. O'Connell, "A Generalized Method for Predicting Second Virial Coefficients," Industrial and Engineering Chemistry Process Design and Development, 14(3), 1975, pp. 209–216.

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