Abstract
Submicron-order pores, such as diatoms in sea-bottom sediments, have large specific surface area and affect the formation and dissociation processes of methane hydrates. We formed synthetic methane hydrates in mesopores of silica gel and diatomaceous earth, and we observed their dissociation process by using calorimetric techniques. The dissociation heat from the methane hydrate in mesopores to gas and ice was about 15% less than that of bulk methane hydrate. Isotopic fractionation of carbon and hydrogen in methane during the formation of hydrate was also investigated. The δD of the hydrate-bound methane was 5.5±0.8‰ lower than that of residual methane in the formation processes, which agrees well with the results of bulk methane hydrate reported in previous research. The δ13C of the hydrate-bound methane was 1.1±0.6‰ higher than that of residual methane; no difference was found in the case of bulk methane hydrate.
