Application of group contribution SAFT equation of state (GC-SAFT) to model phase behaviour of light and heavy esters

The group contribution SAFT approach developed for pure compounds in an earlier work [S. Tamouza, J.-P. Passarello, J.-C. de Hemptinne, P. Tobaly, Fluid Phase Eq. 222–223 (2004) 67] is here extended for the treatment of ester series. Parameters for groups CH 2 and CH 3 previously determined were reused for the alkyl chains while new parameters were determined for COO and HCOO groups. The polarity of these molecules was taken into account by the addition to the equation of state (EOS) of a dipole–dipole interaction term due to Gubbins and Twu [K.E. Gubbins, C.H. Twu, Chem. Eng. Sci. 33 (1978) 863]. This term requires an additional parameter, the dipole moment which was correlated to the COO chemical group position in the ester chain. Three different versions of SAFT were used here to test the validity of the method: the original SAFT [W.G. Chapman, G. Jackson, K.E. Gubbins, M. Radosz, Ind. Eng. Chem. Res. 29 (1990) 1709], VR-SAFT [A. Gil-Villegas, A. Galindo, P.J. Whitehead, S.J. Mills, G. Jackson, A.N. Burgess, J. Chem. Phys. 106 (1997) 4168] and PC-SAFT [J. Gross, G. Sadowski, Fluid Phase Eq. 168 (2000) 183; J. Gross, G. Sadowski, Ind. Eng. Chem. Res. 40 (2001) 1244]. In all three cases, similar and encouraging results are obtained. Reasonable predictions are found on heavy esters that were not included in the regression database.