WOLFRAM|DEMONSTRATIONS PROJECT

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

​
pressure in psi
50
fugacity coefficient
Consider a binary mixture of
n
-butanol and
n
-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 (
76.85%mole
n
-butanol at
14.69psi
), disappears at high pressures (e.g. at
50psi
).
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
P=50psi
is also shown for both the equilibrium curve and the
K
-value for
n
-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
(
B
11
,
B
22
, and
B
12
or
B
21
) 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.