Effects of Additive Mixture (THF/SDS) on the Thermodynamic and Kinetic Properties of CO2/H2 Hydrate in Porous Media

The separation of CO2 from fuel gas (CO2/H-2) as hydrates was studied. In this investigation, the effects and mechanism thereof of the additive mixture (1, 2, 3, and 4 mol % tetrahydrofuran (THF), with 1000 mg/L sodium dodecyl sulfate) on the thermodynamic and kinetic properties of the hydrate in porous media were measured using an isochoric method, keeping the volume constant. The experimental results show that an increasing THF concentration increases the driving force for hydrate formation and decreases the hydrate induction time. The Langmuir constants of H-2 and CO2 showed that H-2 may occupy the small cavities of s-II hydrate in the H-2-CO2-THF-H2O system. The presence of THF results in a drastic decrease of the hydrate phase equilibrium pressure. Higher THF concentrations correspond to lower hydrate phase equilibrium pressures, but the decrease in pressure with concentration slows when the THF concentration exceeds 3 mol %. An improved thermodynamic model was used to predict the hydrate phase equilibrium, and the calculations agreed well with the experimental data.