Thermodynamic studies of CO₂ + TBAB + water system: Experimental measurements and correlations

Thermodynamic properties of TBAB + CO₂ + water system are important for using TBAB + CO₂ semiclathrate hydrates in some promising hydrate-based techniques. This work is an experimental and modeling study of two fundamental properties in vapor-liquid phase equilibrium of TBAB + CO₂ + water, that is, CO₂ solubility in TBAB solution and density of CO₂-saturated TBAB solution. With the use of a PVT system, CO₂ solubility was measured; thus, Henry's constant was obtained at temperatures from 288.1 K to 303.1 K and TBAB mass fraction from 0.10 to 0.40. Our results showed that CO₂ is either salted-in or salted-out by the presence of TBAB, depending upon the temperature and TBAB concentration. For the density, we present experimental data for TBAB + water system at T = 283.15 K to 303.15 K with pressures up to 5 MPa. The density of CO₂-saturated TBAB aqueous solution was calculated with the help of Duan's model, which takes into account the effect of pressure and temperature to calculate the apparent molar volume of dissolved CO₂ in pure water.