Thermodynamic equilibrium data for mixed hydrates of CO2-N2 , CO2-CH4 and CO2-H2 in pure water and TBAB solutions
Abstract
Mixed hydrates containing CO2 and N2, H2 or CH4 have been studied in this paper. Dissociation temperatures as function of the pressure of these hydrates, as well as the dissociation enthalpies, were determined at different gas proportions in pure water and TBAB solutions at 10, 20 30 and 40% using differential scanning calorimetry under pressure.
The addition of TBAB in the solution increases the dissociation temperature of the hydrate and stabilizes it until a certain concentration comprised between 30 and 40 mass percent; after what the temperature decreases. The mixed hydrates of CO2+N2 have a thermodynamic behaviour which is closer to the pure CO2 hydrate at low prerssures; whereas the CO2+CH4 mixed hydrate dissociation temperatures as function of the pressure are quite close when the gas proportion varies. This indicates the selectivity of these mixed hydrates for one gas rather than another which is very useful for separation purposes.