The development of unlike induced association-site models to study the phase behaviour of aqueous mixtures comprising acetone, alkanes and alkyl carboxylic acids with the SAFT-γ Mie group contribution methodology

Abstract

Providing accurate predictions of the thermodynamic properties of highly polar and hydrogen bonding compounds and their mixtures is challenging from a theoretical perspective. The combination of an equation of state (EoS) based on the statistical associating fluid theory (SAFT) with a group contribution (GC) methodology offers both accuracy and predictive capability for the thermodynamic properties of mixtures. In our current work, the SAFT-γ Mie equation of state is used to capture the underlying complexity of systems in which specific interactions (e.g., hydrogen bonding, dipolar interactions, chemical association) play an important role, by incorporating highly versatile association-site schemes to model mixtures in which unlike induced association interactions occur; this is done by assigning to the functional groups a number of association sites that are inactive in the pure fluid, but become active in certain mixtures. We refer to this type of association mechanism as "unlike induced" association and to the sites involved in this interaction as "unlike induced" association sites. The concept of unlike induced association sites is applied here to develop reliable SAFT-γ Mie group contribution models to describe the properties of acetone, alkyl carboxylic acids, and their mixtures with water and n-alkanes. The parameter table of available SAFT-γ Mie models is expanded to incorporate the corresponding group interaction parameters for acetone, which is treated as a molecular group, the carboxyl group COOH, and their unlike interaction group parameters with water, and the methyl CH 3 , methanediyl CH 2 , and methanetriyl CH alkyl groups. In particular, one unlike induced site is used with the acetone model to mediate hydrogen-bonding of the acetone oxygen in mixtures containing hydrogen-bond donors, and two pairs of unlike induced sites are included on the COOH group to mediate hydrogen-bond formation in mixtures of carboxylic acids and hydrogen-bond donors. The models developed allow for the successful description of the complex fluid-phase behaviour of the relevant binary and ternary mixtures, including accurate predictions of systems which have not been used to determine the model parameters.

Modelling and prediction of the thermophysical properties of aqueous mixtures of choline geranate and geranic acid (CAGE) using SAFT-γ Mie

“…The reported values for the vapour pressure and saturated-liquid density, % AAD P vap ¼ 7.96% and % AAD r sat ¼ 3.94%, are slightly higher than the typical % AAD obtained for alkanes and carboxylic acids. 19,36 We note that both the CH] and C] are very small groups with shape factors of 0.20037 and 0.15330, respectively. The small groups thus make a smaller contribution to the thermophysical properties of the solution, and are thus more difficult to characterise.…”

Coarse‐Grained Molecular Simulation of Polymers Supported by the Use of the SAFT‐γ$\gamma$ Mie Equation of State

“…Cross interaction parameters, k ij for the 1:1 mapping for PS and PP are given in Section S2, Supporting Information; b) Acetone is not modeled with only dispersions, and it is modeled as an associating molecule with parameters previously published in ref. [120].…”

“…An accurate phase diagram of the mixture was only calculated for PS-CG1, with k ij = −0.007. The parameters for acetone were taken from elsewhere, [120] without any fitting.…”

Accounting for cross association in non-self-associating species using a physically consistent SAFT-VR Mie approach

“…Physically consistent approaches have been used in select applications of the CPA [21], GCA [22], GC-SAFT [23,24], PC-SAFT [25,26] and SAFT-γ-Mie [27] equations of state, where a range of Type II components have been successfully modelled by considering proton acceptor sites only.…”

“…of Sadeqzadeh et al [27] omits an explicit polar term. Instead, they considered acetone to have both a proton donor and a proton acceptor site in the pure component form, with an additional proton acceptor site being "activated" in appropriate mixtures.…”