THF-CH₄ Hydrate Formation under Static Conditions with the Change of Temperature: Application to CH₄ Storage in the Form of Gas Hydrates

The hydrate-based solidified natural gas technology offers a promising approach to the storage and transportation of natural gas. A key challenge of this technology is to achieve mild hydrate formation conditions and high gas storage capacity. In this work, the effects of temperature on THF-CH4 hydrate formation under static conditions were investigated from multiple perspectives including kinetic measurement, thermal analysis, morphology observation, and in situ Raman spectroscopy. Moreover, the storage stability of THF-CH4 hydrate above the freezing point was explored. The results indicate that 288.15 K is a preferable temperature for increasing the gas uptake of THF-CH4 hydrate formation among the tested temperatures (280.15, 288.15, and 293.15 K), and the highest gas uptake of 0.0756 mol of gas/mol of water was achieved. The continued growth of cloud-like hydrates in the liquid phase was observed, which enhances CH4 diffusion for further hydrate growth. In situ Raman spectroscopy measurement revealed a two-stage growth mechanism in the formation of THF-CH4 hydrate. THF-CH4 hydrate can be stably stored at atmospheric pressure and 277.15 K, with only a 3% gas evolution from the hydrate. The results presented in this work will provide valuable insights for improving the solidified natural gas storage and transportation technology.