Dissociation Kinetics and Metastability of Carbon Monoxide Hydrates Correlating with Phase Change in Water Ice

Abstract

The crystallographic structure of the thermodynamically unstable structure I carbon monoxide (CO) hydrate and its dissociation kinetics were investigated by powder X-ray diffraction and calorimetry. The dissociation of the binary gas hydrates of CO and CH4, CO2, N2, or Ar as secondary guests was also investigated. Here, we observed that the phase transition of ice (amorphous, cubic, and hexagonal ice) formed by CO hydrate dissociation plays a role in the kinetic stability and metastability of the hydrate. Among these gas hydrates, CO + CH4 and CO + CO2 hydrates were preserved at temperatures just below 273 K, which is the self-preservation phenomenon. These results contribute to a comprehensive understanding of the dissociation mechanism of gas hydrates below the melting point of ice, which is crucial for understanding the kinetic stability of naturally occurring gas hydrates in the universe, as well as gas storage by gas hydrates under thermodynamically metastable conditions.