n - PATh :.: Process and Product Applied Thermodynamics research ...

Modeling
shown such wide and reliable applicability to the calculation of vapor-liquid equilibria
(VLE) for systems containing light hydrocarbons, permanent gases, carbon dioxide, and as
shown here, perfluoroalkanes.
P / MPa
12
10
8
6
4
2
0
0 0.2 0.4 0.6 0.8 1
x, y CO2
Figure III.17. Vapor-liquid equilibrium of CO2/perfluoromethylcyclohexane system at 293.15K,
323.15K and 353.15K. Legend as in Figure III.16.
As a further test of the reliability of the parameters provided here for the soft-SAFT
EoS, the performance of the soft-SAFT equation was checked, without and with the
quadrupolar term for the mixture CO2/perfluoro-n-hexane, for which there is available data
in the literature (Iezzi et al, 1989). Figure III.19 shows predictions of the original and the
polar soft-SAFT equation for this mixture. Figure III.19a depicts pure predictions from the
two versions of the equation. Figure III.19b presents calculations from both versions of
soft-SAFT with the size binary parameters taken from Table III.8, and binary size energy
parameters equal to 0.807 and 0.916, respectively. The energy parameters were fitted at
314.65K and used in a transferred manner for the higher temperature, 353.25K. Regarding
the pure predictions (Figure III.19a) it is interesting to see the effect the addition of the
quadrupole has in accurately describing the behaviour of the mixture as compared to the
original equation. The simulation results obtained by Cui et al. (1998) and also by Zhang
and Siepmann (2005) from Monte Carlo simulations for this mixture lye between
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