Prediction of surface properties of binary, sulfur containing mixtures

This work aims to the prediction of the surface tensions of binary mixtures relevant to enhanced oil recovery or bio gas production, in the case, where no or only a very limited number of experimental data are available in the open literature, especially for mixtures, where sulfur-containing compounds are present. We focus our attention to mixtures made of CO2 + SO2 and CO2 + H2S. The predictions were performed with help of density gradient theory (DGT) combined with the perturbed chain statistical associating fluid theory (PC-SAFT) in order to model phase behavior and interfacial properties, simultaneously. The employed PC-SAFT-EOS is able to calculate the phase diagram close to experimental data taken from the literature. The influence parameter of the pure components, required in the DGT-approach, was fitted to the surface tension at one temperature. For the estimation of the influence parameter of the mixture the geometrical combining rule was applied. Additionally, density profiles and consequently, enrichments effects in the surface were calculated. Finally, polynomial expressions for the surface tension as function of the liquid composition and temperature are provided.