PHASE-EQUILIBRIA IN AQUEOUS SYSTEMS FROM AN EQUATION OF STATE BASED ON THE CHEMICAL APPROACH

A previously proposed equation of state incorporating association (AEOS) has been modified to extend its applicability to aqueous systems. The equation consists of two terms: a chemical one based on a generalized association model and a physical one which is equivalent to an equation of state for a monomeric fluid and is represented by a cubic equation of state for nonpolar compounds. The assumptions that are necessary to separate these terms have been discussed. The equation is able to represent simultaneously vapor-liquid and liquid-liquid equilibria in aqueous hydrocarbon mixtures with only one adjustable binary parameter. A well-defined linear temperature dependence of the binary parameter makes it possible to reproduce VLE and LLE over large temperature and pressure intervals with good accuracy.