Phase Equilibrium Modelling for Mixtures with Acetic Acid Using an Association Equation of State

Abstract

Acetic acid is a very important compound in the chemical industry with applications both as solvent and intermediate in the production of, e.g., polyesters. The design of these processes requires knowledge of the phase equilibria of mixtures containing acetic acid and a wide variety of compounds over extended temperature and pressure ranges. From the scientific point of view, modeling of such equilibria is challenging because of the complex association and solvation phenomena present. In this work, a previously developed association equation of state (cubic-plus-association, CPA) is applied to a wide variety of mixtures containing acetic acid, including gas solubilities, cross-associating systems (with water and alcohols), and polar chemicals like acetone and esters. Vapor-liquid and liquid-liquid equilibria are considered for both binary and ternary mixtures. With the exception of a somewhat inferior performance for the water-acetic acid VLE, which does not seem to affect substantially the performance for the multicomponent systems studied, CPA performs satisfactorily in most cases, using a single interaction parameter over extensive temperature ranges. For accurate description of water-acetic acid, use of the Huron-Vidal mixing rule for the energy parameter of CPA can yield a satisfactory correlation at the cost of more interaction parameters.

Thirty Years with EoS/GE Models—What Have We Learned?

“…The Huron−Vidal mixing rule has been recently combined with an association model (CPA) in order to improve the performance of the association model for water−acetic acid VLE. 97 It is important to emphasize that the most successful results with the SRK/ Huron−Vidal model are obtained when a "purely energetic" activity coefficient model is used, for example, NRTL or the residual term of UNIQUAC, UNIFAC, or ASOG, as also illustrated recently by Soave 98 in a successful SRK/HV model using the residual term of the UNIFAC/ASOG models. We have demonstrated in section 2 that this choice of activity coefficient model is consistent with the Huron−Vidal derivation.…”

(Liquid+liquid) equilibria in ternary aqueous mixtures of phosphoric acid with organic solvents at T=298.2K

“…We have recently reported [21] LLE results for the aqueous mixtures of phosphoric acid with 1-butanol and butyl acetate at T = 308.2 K, where a Type 1 (liquid + liquid) phase diagram was obtained for both the ternary systems. As a continuation of that previous work, we present the LLE results for the three ternary systems (water + phosphoric acid + cyclohexane), (water + phosphoric acid + isobutyl acetate), (water + phosphoric acid + 2-methyl-2-butanol) at T = 298.2 K. These organic solvents widely used as extractants to determination of LLE data for many ternary mixtures [22][23][24][25][26][27][28][29].…”

Dimerization of Carboxylic Acids: An Equation of State Approach

“…[20][21][22] In order to describe thermodynamic properties of organic acids, two association schemes are mainly used in the framework of the aforementioned thermodynamic models: the so called "1A" and "2B" association schemes. [23][24][25][26] According to the first one, every acid molecule has one association site, positive or negative, which can be bonded with the relevant site of another acid molecule. The latter one allows the modelling of linear hydrogen bonded oligomers and is, thus, a simplified way of describing carboxylic acid systems.…”

“…[27][28][29][30] Most often, in order to test the validity of a model, its predictions are compared solely to phase equilibrium data. 3,[20][21][22][23][24][25][26] Such kind of predictions are very useful in designing applications, where models are applied to predict the phase behavior of multicomponent mixtures. However, in some cases, the accurate prediction of thermal properties, such as the mixing enthalpies, is also important for a successful prediction of the energy demands.…”