Water/Hydrocarbon Phase Equilibria Using the Thermodynamic Perturbation Theory

Abstract

Two equations of state, the cubic plus association (CPA) and the statistical associating fluid theory (SAFT), which account explicitly for the effect of hydrogen bonding on the thermodynamic properties of associating fluids using the perturbation theory of Wertheim (J. Stat. Phys. 1986, 42, 459, 477), are applied to predict the phase equilibrium of pure water, n-alkanes, and 1-alkenes as well as the low-and high-pressure phase equilibrium of water/hydrocarbon mixtures. The pure compound parameters for the two equations are estimated by fitting experimental vapor pressure and saturated liquid density data that cover a very wide temperature range from approximately the triple point to very close to the critical point. One temperature-independent binary interaction parameter is calculated for each of the mixtures examined. The analysis of the results shows that the increased complexity of SAFT over CPA does not offer any improvement in modeling highly nonideal fluid behavior, at least for the systems examined here.

Solubilities of hydrofluorocarbons in ionic liquids: Experimental and modelling study

“…The Cubic-Plus-Association (CPA) EoS proposed by Kontogeorgis et al [36] can be expressed in terms of the compressibility factor Z which combines the simplicity of a cubic equation of state, the Soave-Redlich-Kwong (SRK EoS), that takes into account the physical interactions between the components, and an advanced associating term described by the Wertheim theory, which accounts for the specific association parameters [37][38][39]:…”

Mutual solubilities of hydrocarbons and water with the CPA EoS

“…The CPA equation of state, in terms of the compressibility factor, can be expressed as the sum of two contributions: one accounting for physical interactions, that in the current work is taken as the SRK EoS, and another accounting for association, the Wertheim association term [22,28,34]:…”

“…However, the original SAFT approach has problems in describing aqueous solutions of hydrocarbons. As shown by Economou and co-workers [5,22], increasing the complexity of SAFT and explicitly accounting for hydrogen bonding, by several mixing rules and association schemes for water, does not improve the fitting of the water solubility neither provide a quantitative description of the hydrocarbon solubility. Possible explanations for the SAFT limitations in these systems are its inadequacy to account for the high polarity of the water molecule, or the use of inappropriate water parameters.…”

Multi-component droplet growth. I. Experiments with supersaturated n-nonane vapor and water vapor in methane

“…From this averaged temperature and pressure an average equilibrium fraction is calculated using the CPA eos ͑cubic plus association equation of state͒, for each condition considered. [13][14][15] Then, a line is drawn from this equilibrium fraction through the experimental data. Within the accuracy of the experiments, this is possible for all experimental conditions investigated.…”