The search for highly absorbents or adsorbents for CO2 has become of increasing interest in the scientific community due to global warming. Among the different possibilities, it has been proved that CO2 increases its solubility in the presence of fluorinated compounds, leading to further investigations in this area. In addition, highly fluorinated molecules are versatile compounds that can be applied to a large number of applications in different research fields. From the molecular point of view, fluorinated compounds are fascinating systems since besides being structurally similar to alkanes their behavior is far from being similar.

We will present a systematic thermodynamic study of the perfluoralkanes family and its mixtures with CO2. The use of a molecular based equation of state (EoS), the soft-SAFT EoS [1], permits to explore a wide range of properties and regions of the phase diagram with the same tool and set of parameters. In particular, phase equilibrium diagrams of perfluoroalkanes and CO2 will be shown; special attention will be paid to the critical region, as a renormalization-group term in the equation allows quantitative predictions of this region [2]. Interfacial properties are also estimated by the combination of the density gradient theory with soft-SAFT [3]. Finally, the equation is also employed to estimate derivative properties such as heat capacities, compressibilities and speed of sound. A comparison with experimental data and some illustrative examples will be presented.

This work was partially funded by the Spanish Government (project CTQ2005-00296/PPQ) and the Catalan Government (2005SGR-00288)

References

[1] F.J. Blas, L.F. Vega, Mol. Phys. 92, (1997) 135-150

[2] F. Llovell, J.C. Pāmies, L.F. Vega, J. Chem. Phys. 121 (2004), 10715-10724

[3] D. Duque, J.C. Pāmies, L.F. Vega, J. Chem. Phys. 121 (2004) 11395-11401