Details

The Peng–Robinson equation of state for mixtures is used to plot pressure versus volume on a log-log graph:

,

where is the gas constant (), is temperature (K), is in MPa and is in .

is the attraction parameter and is the repulsion parameter for the mixture:

,

,

where is the component mole fraction, is the binary interaction parameter and and are the attraction and repulsion parameters for a pure component.

The binary interaction parameter can be calculated [1]:

,

for an alkane/alkane mixture and .

The attraction and repulsion parameters for a pure component are:

,

,

where is the critical temperature (K) and is the critical pressure (MPa).

,

where is a simplification term and is the acentric factor.

Raoult's law is used to calculate the pressure of the mixture at VLE:

,

and is used to determine the vapor mole fraction:

,

where and are the liquid and vapor mole fractions of hexane, and is the saturation pressure that is calculated using the Antoine equation:

,

where , and are Antoine constants.

The screencast video at [2] explains how to use this Demonstration.

References

[1] A. O. Elnabawy, S. K. Fateen and M. M. Khalil, "Semi-empirical Correlation for Binary Interaction Parameters of the Peng–Robinson Equation of State with the van der Waals Mixing Rules for the Prediction of High-Pressure Vapor–Liquid Equilibrium," Journal of Advanced Research, 4(2), 2013 pp. 137–145. doi:10.1016/j.jare.2012.03.004.

[2] Peng-Robinson Equation of State for Mixtures [Video]. (Sep 1 2016) www.colorado.edu/learncheme/thermodynamics/PengRobinsonEOSMixtures.html.