Prediction of aliphatic and aromatic oil-water interfacial tension at temperatures >100 °C using COSMO-RS

As a contribution to the 9th Industrial Fluid Property Simulation Challenge on predicting interfacial tension between water and a set of non-polar oils at temperatures up to 170 °C we have used our first-principles based model, which is based on density functional theory and uses COSMO-RS implicit solvent model thermodynamics. Our calculations predict that the oil-water interfacial tension starts to drop significantly for alkanes at temperatures above ∼100 °C, and the oil-water interfacial tension drops significantly with increased temperature already above ∼25 °C for aromatic oils. In the range 110-170 °C, the interfacial tension drops almost linearly with temperature at a rate of about −0.082 mN/m/K for dodecane and −0.147 mN/m/K for toluene. Our method predicts that for any mix of dodecane and toluene, a linear interpolation of the interfacial tension with respect to the composition is a good approximation. The agreement of our predictions with the experimental data was overall satisfying, apart from a significant difference in the temperature dependence of the dodecane-water interfacial tension. We provide results derived from other experimental measurements suggesting that the large decrease measured by the challenge organizers may be erroneous.