Applications of SAFT to Polar and Associating Mixtures

Abstract

It could be argued that the majority of the applications of SAFT variants are found in the field of nonassociating mixtures, especially polymer solutions and blends (Chapter 14). A few applications for associating mixtures were developed in the decade 1990-2000, but since then the number of applications for associating mixtures has increased substantially and some characteristic publications are summarized in Table 13.1. Mostly, applications to aqueous mixtures as well as systems with alcohols and organic acids have been considered. Few publications deal with multifunctional chemicals such as glycols and alkanolamines, while non-associating polar chemicals (ketones, esters, nitriles, etc.) have also been considered (in most cases with polar and sometimes quadrupolar/induction terms being added). Comparisons against other models, especially the CPA, ESD and NRHB EoS, have been presented in the literature. From a scientific and development point of view, the nature of association schemes and the combining rules for solvating/cross-associating mixtures are worthy of investigation. We will illustrate the major conclusions and present some typical results for some of these applications, roughly divided according to the associating compound considered. Water-hydrocarbonsAqueous systems with hydrocarbons have been studied with various SAFT models with varying degrees of success. There is some disagreement in the overall assessment of the model in the various publications. The different performance of SAFT variants for water-hydrocarbons may be due to details of the specific SAFT model investigated (sites of water, mixing rules, which dispersion term is used, etc.) but they seem more to be due to the parameterization for water, i.e. determination of pure water parameters. The major findings in water-hydrocarbon studies are summarized below in chronological order:1. The first investigations with the original SAFT 9,46 for water-alkanes indicate that SAFT has severe difficulties in representing both water and alkane solubility with the same interaction parameter (k ij ).