Mixed Methane/Dioxane Hydrate Formation in Seawater for Solidified Natural Gas Storage

Global natural gas consumption has shown a general upward trend over the past few decades and continues to increase. Solidified natural gas (SNG) has carved a niche for stationary, large-scale, and long-term storage of natural gas. Herein, we employed 1,3-dioxane as a less toxic and less volatile thermodynamic additive to promote the formation of sII methane hydrate in seawater. The experiments were conducted to investigate the temperature effect on induction time, hydrate formation rate, and gas storage capacity across a broad range from 283.15 to 293.15 K. The growth behavior of hydrate crystals under different temperature conditions was also illustrated. Furthermore, we evaluated various pressure effects (7.5, 9.5, and 11.5 MPa) on hydrate formation in seawater while maintaining a constant temperature. Finally, the impact of three amino acids (l-tryptophan, l-leucine, and l-methionine) on hydrate formation was explored under 288.15 K and 11.5 MPa. The results revealed that a higher subcooling degree or higher driving force improves the kinetics of mixed CH4/dioxane hydrate formation in seawater. Among the amino acids tested, l-tryptophan demonstrated superior performance in enhancing gas storage capacity compared to l-leucine and l-methionine. The findings obtained in this work contribute to the development of environmentally benign SNG technology with efficient utlization of seawater.