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[MIS21-01] Equilibrium pressure of clathrate hydrates encaged 13CH4
Keywords:gas hydrate, methane hydrate, equilibrium pressure, stable isotope
Methane hydrate samples were synthesized in small pressure cells (volume: 5 mL). Fine ice powder (1g) was put in a pressure cell, and introduced 13CH4 (purity: 99.5%, Taiyo-Nissan). Clathrate hydrate was formed by melting the ice powder at the temperature of 273.2K under high pressure of methane. We also prepared normal methane (purity: 99.99% for methane, but 98.9% for 12CH4, Takachiho Chemical Industry Co. Ltd.) hydrate as a reference, using the same preparation method. These pressure cells were placed in a temperature-controlled liquid bath, and measured their equilibrium pressures from 269.5K to 277.9K.
The difference in equilibrium pressure between 13CH4 and normal methane (mainly 12CH4) hydrates was smaller than the measurement error. This results agree with the previous report by Hachikubo et al. (2007).
Ozeki T, Kikuchi Y, Takeya S, Hachikubo A (2018) Phase equilibrium of isotopologue methane hydrates enclathrated CH3D and CD4. J Chem Eng Data 63(6): 2266-2270, doi: 0.1021/acs.jced.8b00203
Hachikubo A, Kosaka T, Kida M, Krylov A, Sakagami H, Minami H, Takahashi N, Shoji H (2007) Isotopic fractionation of methane and ethane hydrates between gas and hydrate phases. Geophys Res Lett 34: L21502. doi:10.1029/2007GL030557