Accounting for cross-association in nonself-associating species using SAFT-VR Mie: Application to mixtures with esters

This work is a continuation on our previous contribution [Cripwell et al., Fluid Phase Equilibria 483 (2019): 1–13] that presented a formalised approach for cross-association in the SAFT-framework. The cross-association, or solvation, of nonself-associating ester molecules is specifically considered here for further development of an approach that is predictive (i.e., independent of system specific kijs) and can be used beyond the systems considered in the initial development of the approach. The accurate dipolar SAFT-VR Mie-GV equation of state is used as the overarching framework to model the esters. A single electron pair donor site (denoted as the N scheme) is assigned to the ester to account for cross-association without false description of self-association. The two association parameters are discretised and ester + alcohol mixture VLE is calculated at each point. The resulting AAD contour plots are utilised to develop a simple correlation, which is based on the molecular weight of the ester, to calculate suitable association parameters. The suitability of this correlation is tested over extended temperature and pressure ranges, and is also shown to extrapolate well to mixtures containing esters and/or alcohols not included in the correlation development. Lastly, ester + chloroform mixtures are also predicted well, supporting the validity of the approach.