Modeling of the Thermodynamics of the Acetic Acid−Water Mixture Using the Cubic-Plus-Association Equation of State

The cubic-plus-association (CPA) equation of state is applied in this work to mixtures containing acetic acid and water. A previously developed modification of the model, the so-called CPA-Huron−Vidal (CPA-HV), is used. New CPA parameters have been estimated based on the vapor pressure, liquid density, enthalpy of vaporization, and vapor-phase compressibility factor data.

The CPA-HV parameters have been fitted to, among others, experimental vapor compressibility factor data and experimental relative volatility data at different temperature ranges. The purpose of the work was to investigate whether the CPA-HV model can describe the vapor−liquid equilibrium for acetic acid−water over a temperature range of 200 K and at the same time represent the behavior of pure acetic acid and acetic acid−water mixtures with respect to enthalpies of vaporization and compressibility factors.

It is shown that satisfactory results are overall obtained, but if an excellent match is needed over the whole temperature range, then different interaction parameters need to be used at the various temperature ranges.