Stable Isotope Fractionation of Nitrogen between Gas and Hydrate Phases

Hachikubo, Akihiro; Takizawa, Kaede; Takeya, Satoshi

doi:10.1021/acs.jced.2c00568

Cited by 2 publications

(2 citation statements)

References 23 publications

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“…Researchgrade methane (99.99% purity; Takachiho Chemical Industrial, Tokyo, Japan) was used as the guest gas. In the synthesis process, fine ice powder (0.1 g), with a specific surface area of 350−450 m 2 kg −1 , 34 was placed in the cell, and the air within the cell was evacuated at 77 K. Methane was then introduced into the cell, which was either placed in a cold room (226, 246, and 255 K) or immersed in a temperature-controlled liquid bath (273 K). Methane hydrate formation occurred with approximate formation times of 1 day (246, 255, and 273 K) and 1 week (226 K).…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Effect of Temperature and Pressure on the Hydration Number of Methane Hydrate

Hachikubo,

Kida,

Yahagi

et al. 2024

Energy Fuels

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Methane hydrates contain a certain number of empty cages that affect their stability and determine the gas-storage capacity of the material. In this study, the effects of temperature and pressure on the hydration number of methane hydrates were investigated in pressure and temperature ranges of 0.53−20.50 MPa and 226−273 K, respectively. Raman spectroscopy measurements showed that the hydration number ranged from 5.88 to 6.12, decreasing with increasing pressure and decreasing temperature. The occupancy of the large cages ranged from 97 to 99%, indicating that most of the cages were occupied. In contrast, small cage occupancy ranged from 82 to 96%, suggesting that small cage occupancy was significantly reduced under high-temperature and lowpressure conditions. The results of this study experimentally demonstrate the change in cage occupancy of methane hydrates as a function of formation temperature and pressure and will help future researchers comprehend not only the cage occupancy of host−guest compounds but also the amount of methane resources on earth.

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Section: ■ Experimental Methodsmentioning

confidence: 99%

Effect of Temperature and Pressure on the Hydration Number of Methane Hydrate

Hachikubo,

Kida,

Yahagi

et al. 2024

Energy Fuels

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“…The hydrogen isotope ratio of the hydrate-bound gas is several ‰ lower than that of the residual gas [9], whereas stable isotope fractionation is negligible in terms of carbon isotope ratios [9,10]. Such stable isotope fractionation of guest gases during gas hydrate formation has been similarly investigated for ethane [9], carbon dioxide [11,12], hydrogen sulfide [13], and nitrogen [14].…”

Section: Introductionmentioning

confidence: 99%

Effect of Pressure on Hydrogen Isotope Fractionation in Methane during Methane Hydrate Formation at Temperatures Below the Freezing Point of Water

Hachikubo

Nezu

Takizawa

et al. 2023

Methane

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Isotopic fractionation of methane between gas and solid hydrate phases provides data regarding hydrate-forming environments, but the effect of pressure on isotopic fractionation is not well understood. In this study, methane hydrates were synthesized in a pressure cell, and the hydrogen isotope compositions of the residual and hydrate-bound gases were determined. The δ2H of hydrate-bound methane formed below the freezing point of water was 5.7–10.3‰ lower than that of residual methane, indicating that methane hydrate generally encapsulates lighter molecules (CH4) instead of CH32H. The fractionation factors αH-V of the gas and hydrate phases were in the range 0.9881–0.9932 at a temperature and pressure of 223.3–268.2 K and 1.7–19.5 MPa, respectively. Furthermore, αH-V increased with increasing formation pressure, suggesting that the difference in the hydrogen isotopes of the hydrate-bound methane and surrounding methane yields data regarding the formation pressure. Although the differences in the hydrogen isotopes observed in this study are insignificant, precise analyses of the isotopes of natural hydrates in the same area enable the determination of the pressure during hydrate formation.

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Stable Isotope Fractionation of Nitrogen between Gas and Hydrate Phases

Cited by 2 publications

References 23 publications

Effect of Temperature and Pressure on the Hydration Number of Methane Hydrate

Effect of Temperature and Pressure on the Hydration Number of Methane Hydrate

Effect of Pressure on Hydrogen Isotope Fractionation in Methane during Methane Hydrate Formation at Temperatures Below the Freezing Point of Water

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