Water/hydrocarbon phase equilibria using the thermodynamic perturbation theory

Two equations of state, the cubic plus association (CPA) and the statistica l associating fluid theory (SAFT), which account explicitly for the effect of hydrogen bonding on the thermodynamic properties of associating fluids u sing the perturbation theory of Wertheim (J. Stat. Phys. 1986, 42, 459, 477 ), are applied to predict the phase equilibrium of pure water, n-alkanes, a nd 1-alkenes as well as the low- and high-pressure phase equilibrium of wat er/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 th e triple point to very dose to-the critical point. One temperature-independ ent binary interaction parameter is calculated for each of the mixtures exa mined. The analysis of the results shows that the increased complexity of S AFT over CPA does not offer any improvement in modeling highly nonideal flu id behavior, at least for the systems examined here.