Molecular Insights into Methane Hydrate Formation in Hydrogen Oxide, Deuterium Oxide, and Tritium Oxide

Hydrate-based methods are a potential technique for methane storage, and the addition of deuterium oxide (D2O) may improve methane hydrate storage. In this work, methane hydrate formation in hydrogen oxide (H2O), deuterium oxide (D2O), and tritium oxide (T2O) was simulated using Gromacs software. The four-body structural order parameter (F4), hydrate formation and growth, and total energy were analyzed. These results suggested that variations in both the F4 value and total energy can be used to determine the formation of CH4 hydrates. The formation rate of CH4 hydrates in T2O was faster than that in D2O and H2O. For CH4 conversion at 2000 ns, (CH4 + D2O) is 1.70 times greater than that in (CH4 + H2O) hydrates. Based on both CH4 hydrate growth and CH4 conversion, (CH4 + D2O) hydrates are superior to (CH4 + H2O) hydrates for CH4 storage. (CH4 + T2O) hydrate is 2.25 times that of (CH4 + H2O) hydrates, which also offer useful insights for H2O/D2O separation and even nuclear wastewater treatment. In addition, the primary structure of CH4 hydrate in H2O, D2O, and T2O is of the SI type, with occasional occurrences of SII- and even SH-type hydrates. The presence of numerous unconventional hydrate cages may facilitate the formation of conventional hydrate cages.