Investigation of gas hydrate formation method based on polymer matrices under a non-stirred system

Abstract

Clathrate hydrate is a crystalline compound stabilized by van der Waals interactions between entrapped small molecules (e.g., gas, hydrocarbon) inside 3-dimensional hydrogen bonding network and host water molecules. In this thesis, the methods of clathrate hydrate formation without energy-intensive mechanical agitation were investigated by utilizing different polymer matrices. Variety of polymer matrices and thermodynamic promoters were utilized to obtain optimal methane storage capacity and kinetics, and energy-saving methane storage process via hydrate formation was suggested. The contents of each chapters are as follows. In Chapter 2, superabsorbent polymers (SAPs) and thermodynamic promoters were employed to store methane and carbon dioxide in clathrate hydrates. Due to large surface area from interstitial voids between hydrogels, the hydrates were immediately nucleated even without stirring, and occurrence of tuning effect that gas molecules occupy $5^{12}6^4$ cages of hydrates was confirmed. In Chapter 3, hydrogels from superabsorbent polymers and thermodynamic promoters were applied to repetitive methane hydrate formation process. At different pressure and temperature conditions, this process was thoroughly investigated in terms of methane storage capacity and kinetics. With proceeding of cycles, the changing trends of methane uptake and kinetics were varied by loss of thermodynamic promoters. In Chapter 4, a melamine sponge and low dosage of promoters were employed to obtain higher methane uptake and faster kinetics. A variety of combinations between thermodynamic and kinetics promoters were optimized with regard to methane uptake, kinetics, and sustainability, and optimal combination of promoters was suggested.