Application of MOSCED To Predict Limiting Activity Coefficients, Hydration Free Energies, Henry’s Constants, Octanol/Water Partition Coefficients, and Isobaric Azeotropic Vapor–Liquid Equilibrium

Abstract

Modified Separation of Cohesive Energy Density (MOSCED) is a solubility parameter-based method to predict limiting activity coefficients. In addition to making quantitative predictions, MOSCED may additionally be used to understand the underlying molecular-level driving forces for intuitive solvent selection and formulation. A major improvement of MOSCED over similar solubility parameter methods is that it splits the association term. We show by example how this change allows MOSCED to better model the molecular interactions of associating fluids. While parametrized to predict limiting activity coefficients, we demonstrate the ability to predict hydration-free energies, Henry’s constants in water, and octanol/water partition coefficients. We focus on water as MOSCED was previously found to perform substantially worse when water was the solvent. Comparison is made to molecular simulation and mod-UNIFAC, and we find for the studied reference set that predictions with MOSCED were in better agreement with experimental data. Comparison to mod-UNIFAC was additionally made to model binary isobaric azeotropic vapor–liquid equilibrium. Overall, for these nonideal systems, the quantitative agreement with experiment is better with mod-UNIFAC, although the difference with MOSCED is relatively small. An interactive software suite (MOSCED-CAD) has also been developed to calculate the properties described in the present study, in addition to binary interaction parameters for the Wilson and the nonrandom two-liquid (NRTL) equations for use in a process simulator.

Assessment of the SM12, SM8, and SMD Solvation Models for Predicting Limiting Activity Coefficients at 298.15 K

“…Brouwer and Schuur [72] recently conducted a comparative study of eight predictive methods to compute ln γ ∞ i,j at 298.15 K. Of the methods evaluated, the solubility parameter method MOSCED was the top performer. This strong performance of MOSCED is consistent with the findings of the 2005 re-parameterization [20,73] and our recent work [8,74]. MOSCED was therefore selected as an additional comparison alongside UNIFAC.…”

“…The applications are vast for they are used in the design of separation equipment, solvent selection, the design of pharmaceuticals, stripping operations, leaching operations, and the extraction of dilute materials [2,3]. Previous studies have also shown that activity coefficients can be used to predict the formation of an azeotrope [4][5][6][7][8]. The equilibrium composition of a dilute mixture can be also be determined, thus having industrial applications in azeotropic distillation and high-purity extraction [9].…”

“…For example, limiting activity coefficients can be used to determine partition coefficients for a dilute species between two phases, which is critical in predicting the bio-accumulation of long-lived chemicals in the environment and food chain [2]. Furthermore, limiting activity coefficients of each component in a binary mixture can be used to parameterize binary interaction excess Gibbs free energy models to make phase equilibrium calculations over an entire range of concentrations [8,[11][12][13]. These parameterizations are particularly advantageous for maximizing the efficiency of separation processes, which comprise a large majority of chemical plant operations and costs.…”

“…Similarly, mod-UNIFAC (Dortmund) is a revision of the original UNIFAC model that accounts for the temperature dependence of activity coefficients by including temperature-dependent interaction parameters within the model [17,18]. Solubility parameter based methods such as the modified separation of cohesive energy density (MOSCED) [8,19,20] and Hansen solubility parameter (HSP) methods [21], while they limit the user to modeling systems for which solute parameters are available, they give molecular-level insight into the the behavior of a binary system. Molecular dynamic simulations and electronic structure calculations can be computationally rigorous, yet are advantageous for they only require the input of a molecular structure [22][23][24][25].…”

Infinite Dilution Activity Coefficients as Constraints for Force Field Parameterization and Method Development

“…5 Techniques such as gas-liquid chromatography, 5,10 high-performance liquid chromatography 10 and differential ebulliometry 5,10,11 are traditionally used to measure activities in extremely dilute systems at varying concentrations, leading to the infinite dilution activity coefficient by extrapolation. 10 There has been considerable interest in predicting these coefficients [5][6][7][10][11][12][13][14][15][16][17][18][19][20][21] due to their use in phase equilibria studies in chemical engineering applications. [2][3][4]14 IDACs (also represented by γ ∞ ) are related to solvation free energies by the following equation: 6,7,13…”