An Equation of State Based on PC-SAFT for Physical Solvents Composed of Polyethylene Glycol Dimethylethers

A technical equation of state (EoS), according to the perturbed chain statistical associating fluid theory (PC-SAFT), is developed for solvent blends composed of polyethylene glycol dimethylethers (PEGDMEs/glymes), that is, CH 3 O[CH 2 CH 2 O] n CH 3 with n = 3, ..., 9. These solvent blends are employed in industry under the commercial names Selexol or Genosorb, primarily for the physical absorption of H 2 S and CO 2 from acid gases. The molecular parameters for the EoSs of the pure fluids comprising the solvent, notably for the n = 3 and 4 members of the homologous series, are obtained by fitting the PC-SAFT EoS to published vapor pressure and liquid density data. Because of the limited availability of experimental data for the glymes with n ≥ 5, PC-SAFT is used as a predictive tool to determine the molecular parameters for the n = 5, ..., 9 members of the homologous series. To exploit the extrapolative capabilities of PC-SAFT, the n = 1 and 2 members of the homologous series are included in this study. The mixture of glymes is modeled using the van der Waals one-fluid mixing rules with the Lorentz–Berthelot combining rules, whereby the binary interaction parameters k ij among the members of the homologous series are all set to zero. The performance of the mixture EoS is assessed by a comparison of predicted properties with experimental data. The thermodynamic model is also briefly applied to describe the vapor–liquid equilibrium behavior of glymes and their blends with CO 2 . The comparison with available experimental data shows that the resulting model provides a description of the thermodynamic behavior of this system suitable for engineering purposes.