Phase equilibria of systems containing oxygenated compounds: Polar or “pseudo-association” approach?

Quantifying the effect of polarity on the behavior of mixtures of n‐alkanes with dipolar solvents using polar soft‐statistical associating fluid theory (Polar soft‐SAFT)

“…For mixtures of associating molecules, cross-association interactions between different molecules or different functional groups within the same molecules are computed using combining rules similar to those in Equations (2a) and (2b). In some cases, polar interactions have been implicitly taken into account in SAFT-type equations through the association term, alternatively known as pseudoassociation, 40,[51][52][53][54] however, as this work deals with binary mixtures of nonassociating polar fluids, explicitly using the polar term, with nonassociating fluids, the association term of Equation ( 1) was turned off in our calculations.…”

“…Conversely, a simpler strategy that can help mitigating parameter degeneracy of SAFT models involves fixing some of the molecular parameters which decreases the number of "optimal" sets to fit, either through fixing the dipole moment to that of the experimental moment, 12,26,27,29,39 or fitting the polar parameters and transferring them to the rest of the family such as for 2-ketones. 9,24,40 Extending these models to binary mixtures of dipolar fluids with nalkanes obtained near predictive results, requiring system-specific small values for binary energy interaction parameter (k ij or ξ ij ). However, accurate representation of the LLE behavior of the same mixtures with n-alkanes, especially in the case of those with μ > 2.0 D, either required system-specific binary parameters correlated with the chain length of the n-alkanes, 40 or explicit inclusion of temperature dependency.…”

“…9,24,40 Extending these models to binary mixtures of dipolar fluids with nalkanes obtained near predictive results, requiring system-specific small values for binary energy interaction parameter (k ij or ξ ij ). However, accurate representation of the LLE behavior of the same mixtures with n-alkanes, especially in the case of those with μ > 2.0 D, either required system-specific binary parameters correlated with the chain length of the n-alkanes, 40 or explicit inclusion of temperature dependency. 41,42 Although in these cases, the parametrization framework of the pure dipolar fluids is less complex due to the decreased number of fitted molecular parameters, still it is on the expense of a robust modeling framework when extended to representing the global phase equilibria (i.e., VLE and LLE) for binary mixtures with n-alkanes, requiring different sets of binary parameters to capture the overall phase equilibria.…”

“…Recently, we have extended the soft-SAFT EoS 43,44 to the explicit modeling of polar fluids, namely, polar soft-SAFT EoS. 34 Moreover, we have established a consistent and simplified procedure for the regression of molecular parameters of pure polar fluids, through fixing not only the dipole/quadrupole moment to the experimental value as seen in previous works, 12,24,26,[28][29][30]35,37,40 but also fixing a priori the fraction of polar segments within the molecule (socalled x p parameter). In this manner, the robustness of the model is preserved as only fitting the three nonassociating parameters (m, σ, ε/k B ) is required, similar to the case of nonassociating polar fluids such as polar aprotic solvents.…”

“…Conversely, a simpler strategy that can help mitigating parameter degeneracy of SAFT models involves fixing some of the molecular parameters which decreases the number of “optimal” sets to fit, either through fixing the dipole moment to that of the experimental moment, 12,26,27,29,39 or fitting the polar parameters and transferring them to the rest of the family such as for 2‐ketones 9,24,40 . Extending these models to binary mixtures of dipolar fluids with n ‐alkanes obtained near predictive results, requiring system‐specific small values for binary energy interaction parameter ( k ij or ξ ij ).…”