A Quadrupolar SAFT-VR Mie Approach to Modeling Binary Mixtures of CO₂ or Benzene with n-Alkanes or 1-Alkanols

Abstract

SAFT-VR Mie is extended to quadrupolar molecules and their mixtures by incorporating an explicit Helmholtz contribution for quadrupole−quadrupole interactions. Two quadrupolar terms are considered: the quadrupolar theory of Larsen and coworkers, and that of Gross, yielding VRM-L and VRM-G, respectively. Each model requires an additional parameter for quadrupolar molecules. The two quadrupolar models are evaluated by means of their ability to model the following binary systems: CO 2 or benzene with n-alkanes or 1-alkanols and binary mixtures of quadrupolar molecules. VRM-L and VRM-G offer significant improvements over nonpolar SAFT-VR Mie in describing the VLE of the CO 2 + n-alkane systems, while only the benzene + n-hexane system requires the additional quadrupolar term for accurate description. Cross-association in CO 2 + 1-alkanol systems is accounted for by fine-tuning the association parameters of CO 2 , resulting in an improved description of these systems using VRM-G. Less promising results are obtained with VRM-L. VRM-L and VRM-G can describe benzene + 1-alkanol systems without cross-association. The quadrupolar models can qualitatively represent the VLLE of CO 2 + n-alkane and CO 2 + 1-alkanol systems. Good predictions of the CO 2 + benzene system are obtained with both VRM-L and VRM-G when only CO 2 is modeled as quadrupolar.

Multipolar SAFT-VR Mie Equation of State: Predictions of Phase Equilibria in Refrigerant Systems with No Binary Interaction Parameter

“…Many polar versions of SAFT or CPA have been proposed in the literature. − The main advantage of these polar versions is the ability to explicitly account for electrostatic interactions, allowing for the development of transferable molecular models. Using an explicit multipolar term significantly improves the description of the phase behavior of non-ideal mixtures and often leads to binary interaction parameters ( k ij ) much closer to zero.…”

“…In this work, the M-SAFT-VR Mie model and the polar soft-SAFT EoS are extended to polarizable fluids, and the predictions of the two EoSs are compared with molecular simulation data. Several polar versions of the SAFT-VR Mie EoS have been developed. ,,, The first polar SAFT-VR Mie version was presented by Paricaud et al, and the full expressions of the EoS are presented in this article. The nonpolarizable version of the M-SAFT-VR Mie model is applied to fluorinated refrigerant mixtures without using any binary interaction parameters ( k ij = 0) for all systems and compared to other models such as the E-PPR78 model and the polar soft-SAFT …”

Application of Renormalization Corrections to SAFT-VR Mie

“…The statistical associating fluid theory (SAFT) equation of state (EoS), , which is developed from the first-order perturbation theory of Wertheim, − is a successful thermodynamic modeling tool, which can describe the thermodynamic properties of complex fluids and their mixtures. − Of the SAFT variants, the SAFT with variable range Mie-potential, or SAFT-VR Mie, is arguably the most advanced of the SAFT variants that shows promise as a holistic predictive tool because it offers an improvement of the near-critical region while retaining accurate descriptions of second-derivative properties. , SAFT-VR Mie has already been applied to a wide variety of components and their mixtures, including hydrocarbons, − associating molecules, , aqueous mixtures, , inorganic gases, ionic liquids, and haloalkanes. , SAFT-VR Mie has also been extended to account for dipolar , and quadrupolar , interactions and applied to mixtures containing polar molecules. − In all of these works, it is shown that SAFT-VR Mie offers excellent descriptions of the investigated systems.…”

“…SAFT-VR Mie, however, is not able to describe the exact scaling behavior observed in the near-critical region. As evidenced in a number of investigations, ,,,,,− the model is also unable to capture the critical behavior of mixtures, even when binary interaction parameters are implemented. This is a result of the mean-field approximation (MFA) , in which the wider SAFT framework is rooted.…”

“…32,33 SAFT-VR Mie has already been applied to a wide variety of components and their mixtures, including hydrocarbons, 34−39 associating molecules, 40,41 aque-ous mixtures, 40,42 inorganic gases, 36 ionic liquids, 43 and haloalkanes. 44,45 SAFT-VR Mie has also been extended to account for dipolar 46,47 and quadrupolar 47,48 interactions and applied to mixtures containing polar molecules. 46−50 In all of these works, it is shown that SAFT-VR Mie offers excellent descriptions of the investigated systems.…”