Predicting Limiting Activity Coefficients and Phase Behavior from Molecular Structure: Expanding MOSCED to Alkanediols Using Group Contribution Methods and Electronic Structure Calculations

The modified separation of cohesive energy density (MOSCED) is a powerful tool for early stage process conceptualization and design. It is capable of making quantitative phase-equilibrium calculations, and more importantly may be used to qualitatively understand the underlying molecular level details of a system for intuitive process design. Unfortunately, its use is limited in that parameters must first be known before predictions may be made. Here we explore the use of group contribution methods (GC-MOSCED) and electronic structure calculations in the solvation model based on density (SMD) and SM8 continuum solvation models to calculate missing parameters. We demonstrate the use of GC-MOSCED to expand MOSCED using limited data, and the ability of electronic structure calculations to calculate parameters devoid of experimental data. While GC-MOSCED performs best, we demonstrate that good predictions may be made using electronic structure calculations with the SMD continuum solvation model. Application is demonstrated for limiting activity coefficients and binary isobaric azeotropic vapor–liquid equilibrium with 1,2-ethanediol