Hydrate–based SF6 capture and sequestration: Insights from thermodynamics, kinetics, in–situ Raman spectroscopy, and molecular dynamic simulation

Abstract

Sulfur hexafluoride (SF6) is currently the most potent greenhouse gas to date due to its remarkably long atmospheric lifespan and chemical inertness. Hydrate–based technology provides an innovative solution to capture SF6 under lower pressure conditions and enables the long–term storage of SF6 gas. Herein, we conduct a fundamental study to explore the potential of capturing and sequestering SF6 gas within clathrate hydrates. The three–phase coexistence conditions were measured at the pressure ranging from 0.33 to 1.06 MPa and at ambient temperatures. A thermodynamic model was employed to predict the equilibrium conditions, using an iterative method to calculate the phase equilibrium pressure. Molecular dynamic simulation (MD) was used to observe the growth of SF6 hydrate at the nanosecond scale. In-situ Raman spectroscopy was utilized for analyzing real-time vibrational bands of S–F and O–H in SF6 hydrate, offering crucial insights into hydrate stability and growth. Additionally, microscopic kinetic experiments were also carried out to clarify the impacts of different pressures (0.8, 1.0, and 1.2 MPa) on the nucleation time, gas consumption, and growth rate during hydrate formation in both pure water and seawater. An efficient approach is proposed for the separation of solid–liquid mixtures, fabricating hydrate pellets. The findings of this study establish a foundation for the development of hydrate–based SF6 capture and storage technology.