Modelling gas hydrates in a saline environment for water treatment and CO2 and N2 capture

The study of clathrates as a solution for CO₂ capture and treatment has received significant scientific attention, as has their use in water desalination, a critical issue in many countries due to the scarcity of potable water. This work proposes a thermodynamic modeling approach compared with experimental data for the treatment of clathrate hydrates with N₂–CO₂ gas mixtures, using cyclopentane as an effective promoter. The binary equilibria among the considered substances were studied using the PPR78 model as an alternative to the simple Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK) models. Thanks to the modifications introduced to the PR model, using PPR78 results in absolute standard deviations below 2%, making it an optimal model for the considered binary equilibria. For the modeling of hydrate formation, the van der Waals–Platteuw model was adopted, which, based on the Kihara parameters, allows the analysis of different chemical equilibria under varying pressure and temperature conditions. All binary mixtures of carbon dioxide, nitrogen, and cyclopentane during clathrate hydrate formation were examined, and results comparable with experimental data were obtained only for the binary equilibria containing the promoter; the lack of useful experimental data and computational difficulties prevented tracking the equilibrium behavior of nitrogen and carbon dioxide under varying pressure and temperature. A better estimation of the Kihara parameters and further experiments would allow an efficient analysis of the previously considered equilibrium; with parameter optimization, it would also be possible to consider the ternary complex of guest molecules during clathrate formation and the addition of salts typically present in water to improve the optimization process.