(231b) Solubility of Water in Alkanes, Perfluoroalkanes and Perfluoroalkylalkanes: Experimental Results and SAFT Modeling

The solubility of water in liquid alkanes and their mixtures is of vital importance to the gas and petroleum industries. Preventing corrosion and hydrate crystal formation in subsea and terrestrial pipelines are examples of operating and safety problems, which require a precise knowledge of water content in hydrocarbons. Given the importance of the subject, a large number of results can be found in the literature. However, significant disagreement is found between these results, surely reflecting the difficulty of these measurements.

On the other hand, the mutual (im)miscibility between water and perfluoroalkanes or perfluoroalkylalkanes (PFAA) has a very important role in their biomedical applications, and also in their use in biphasic synthesis and catalysis. Moreover, it has been demonstrated that the presence of water is fundamental for the processes of self-organization and nano-pattern formation in molecular films of PFAA.

In this work, new experimental results for the solubility of water in liquid n-alkanes, perfluoroalkanes, in their mixtures and in perfluoroalkylalkanes, as a function of temperature, will be presented. The corresponding solution thermodynamic quantities are presented and discussed, and suggest a specific interaction between water and PFAA.

The results were modeled using a version of the hetero-SAFT-VR equation that explicitly takes into account the presence of dipoles. The theoretical predictions quantitatively describe the experimental results, and confirm the importance of dipolar interactions in the behavior of water-PFAA systems.