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Prediction of Gas Solubility in Ionic Liquids Using the Cosmo-Sac Model

Jaschik M., Piech D., Warmuziński K., Jaschik J.

Chemical and Process Engineering

2017

Vol. 38, nr 1

19--30

Thermodynamic principles for the dissolution of gases in ionic liquids (ILs) and the COSMO-SAC model are presented. Extensive experimental data of Henry’s law constants for CO2, N2 and O2 in ionic liquids at temperatures of 280-363 K are compared with numerical predictions to evaluate the accuracy of the COSMO-SAC model. It is found that Henry’s law constants for CO2 are predicted with an average relative deviation of 13%. Both numerical predictions and experimental data reveal that the solubility of carbon dioxide in ILs increases with an increase in the molar mass of ionic liquids, and is visibly more affected by the anion than by the cation. The calculations also show that the highest solubilities are obtained for [Tf2N]ˉ. Thus, the model can be regarded as a useful tool for the screening of ILs that offer the most favourable CO2 solubilities. The predictions of the COSMOSAC model for N2 and O2 in ILs differ from the pertinent experimental data. In its present form the COSMO-SAC model is not suitable for the estimation of N2 and O2 solubilities in ionic liquids.

Optimization of the quintic equation of the state based model for the calculations of different thermodynamic properties

Kozioł A., Wiśniewski R.

Polish Journal of Chemical Technology

2008

Vol. 10, nr 1

6-10

Different thermodynamic properties (the vapour density, the liquid density and the saturation pressure) were calculated by the model based on the Nakamura-Breedveld-Prausnitz equation of state (NBP EOS). Since the original form of the NBP EOS often generates inaccurate results for liquids, it was modified to describe this phase better. The calculations were realized in the subcritical region. So far, the temperature-dependent NBP EOS parameters have been obtained by special correlations. Their constants were fitted to a lot of experimental data. In this paper the equation of state temperature-dependent parameters were obtained by a new method which was based at piecewise cubic Hermite interpolating polynomials (PCHIPs). In the proposed method some experimental data (called the key ones) were used, thus reducing the experimental effort. Seven substances were chosen for the test calculations. Each of them is common in industry. The calculation results were compared with the experimental data. The new method has made an accurate description of vapour-liquid equilibrium for the considered pure substances over a wide temperature range possible.