Prediction of Thermodynamic Properties and Phase Behavior of Fluids and Mixtures with the SAFT-γ Mie Group-Contribution Equation of State

Abstract

Group contribution (GC) approaches are based on the premise that the properties of a molecule or a mixture can be determined from the appropriate contributions of the functional chemical groups present in the system of interest. Although this is clearly an approximation, GC methods can provide accurate estimates of the properties of many systems and are often used as predictive tools when experimental data are scarce or not available. Our focus is on the SAFT-γ Mie approach [Papaioannou, V.; Lafitte, T.; Avendaño, C.; Adjiman, C. S.; Jackson, G.; Müller, E. A.; Galindo, A. Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments. J. Chem. Phys. 2014, 140, 054107–29] which incorporates a detailed heteronuclear molecular model specifically designed for use as a GC thermodynamic platform. It is based on a formulation of the recent statistical associating fluid theory for Mie potentials of variable range, where a formal statistical–mechanical perturbation theory is used to maintain a firm link between the molecular model and the macroscopic thermodynamic properties. Here we summarize the current status of the SAFT-γ Mie approach, presenting a compilation of the parameters for all functional groups developed to date and a number of new groups. Examples of the capability of the GC method in describing experimental data accurately are provided, both as a correlative and as a predictive tool for the phase behavior and the thermodynamic properties of a broad range of complex fluids.

Development of intermolecular potential models for electrolyte solutions using an electrolyte SAFT-VR Mie equation of state

“…We consider only aqueous electrolyte solutions and treat the solvent using the Mie model for water based on the Lennard-Jones association kernel developed in earlier work [37,40]. In this model, the water molecule comprises a single segment with four off-centre association sites, two of which are of the hydrogen type 'H' (n H, j = 2) and two of the electron lone-pair type 'e' (n e, j = 2), which mediate hydrogen bonding interactions.…”

“…The novel SAFT-VR Mie EOS has brought a new level of reliability in the development of an accurate platform for the thermodynamic properties of complex fluids and fluid mixtures [36][37][38]. The approach has also been cast as a group-contribution methodology (SAFT-γ ) [39,40], where the molecules are represented in terms of the underlying chemical functional groups, providing an enhanced predictive capability. Importantly, the improved theoretical framework provides models that reflect more accurately the physics of the systems they describe, reducing the reliance on re-adjusting the values of the intermolecular parameters to capture given thermodynamic properties of interest (although, of course, the estimation of the key parameters is still necessary).…”

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

“…Within the SAFT family of EoSs, our focus is on the SAFT-γ Mie [71,72] framework, a group-contribution (GC) reformulation of the SAFT-VR Mie EoS [67] for heteronuclear molecules composed of fused segments. This approach enables the treatment of fluids composed of spheres interacting through a Mie (generalized Lennard-Jones) potential.…”

“…The use of a group contribution concept in the SAFT-γ Mie EoS, with the assumption that the property of any given compound can be obtained from the individual contributions of different chemically distinct functional groups present in the compound leads to a highly predictive and accurate EoS that can be used to obtain the properties of complex mixtures from group models. Importantly, the group parameters are characterized based on appropriate thermophysical data for simple systems (often pure component data alone is enough) but can be used for multifunctional molecules [72].…”

“…The remaining terms correspond to the mean-attractive energy, which is calculated from a knowledge of the contact radial distribution function of the reference hard-sphere fluid at an effective density; the fluctuation term, calculated following the improved macroscopic compressibility approximation proposed by Zhang [86] and a correction of the type proposed by Paricaud [87]; and the third-order term which is represented with an empirical expression based on simulation phase-coexistence data for representative pure Mie fluids. Detailed information about the development of the each if these terms can be found in the original paper [71] and is summarised in reference [72].…”