Reducing the amount of PCP–SAFT fitting parameters. 2. Associating components

The pure-component parameters of the Perturbed Chain Polar-Statistical Associating Fluid Theory (PCP–SAFT) equation of state are preferably fitted to experimental data in broad temperature ranges, if available. In this work, an alternative strategy was developed for estimating the two association parameters. Analysis revealed that the association volume can be set to one common value within a homologous series and the association-energy parameter can be obtained using the hydrogen-bonding enthalpy given by the Conductor-like Screening Model for Real Solvents (COSMO–RS). Thus, the number of fitting parameters was reduced from five to three for associating components. Applying the association parameters obtained from COSMO-RS led to linear molar-mass correlations for the remaining parameters. Moreover, these parameter correlations can be used to further reduce the experimental effort of parameter estimation. Application to the modeling of pure-component properties and binary phase equilibria leads to convincing modeling results.