Carbon Isotope Fractionation during the Formation of CO Hydrate and Equilibrium Pressures of CO and CO Hydrates.

Knowledge of carbon isotope fractionation is needed in order to discuss the formation and dissociation of naturally occurring CO hydrates. We investigated carbon isotope fractionation during CO hydrate formation and measured the three-phase equilibria of CO-HO and CO-HO systems. From a crystal structure viewpoint, the difference in the Raman spectra of hydrate-bound CO and CO was revealed, although their unit cell size was similar.

Temperature effects on the C-H symmetric stretching vibrational frequencies of guest hydrocarbon molecules in 5, 56 and 56 cages of sI and sII clathrate hydrates.

C-H symmetric stretching vibrational frequencies of CH, CH and CH molecules encapsulated in 5, 56 and 56 cages of structures I (sI) and II (sII) clathrate hydrates measured by Raman spectroscopy in the temperature range of 93-183 K was analysed. The slopes of the symmetric stretch vibrational frequencies under changing temperatures (Δ/Δ) for CH, CH and CH molecules encapsulated in sII 56 cages were smaller than those for molecules in sI 56 cages, although sI 56 cages are smaller than sII 56 cages. We compared the results of Δ/Δ in this study with the geometrical properties of each host water cage, and these comparisons suggest that the geometry of host water cages affects Δ/Δ.

Effect of temperature and large guest molecules on the C-H symmetric stretching vibrational frequencies of methane in structure H and I clathrate hydrates.

Large molecules such as 2-methylbutane (CH) or 2,2-dimethylbutane (CH) form structure H (sH) hydrates with methane (CH) as a help gas. In this study, the Raman spectra of the C-H symmetric stretch region of CH enclathrated within various sH hydrates and structure I CH hydrates were analyzed in the temperature range 137.7-205.

Retraction: Effect of temperature and large guest molecules on the C-H symmetric stretching vibrational frequencies of methane in structure H and I clathrate hydrates.

[This retracts the article DOI: 10.1039/C7RA12334E.].

Retracted Article: Effect of temperature and large guest molecules on the C-H symmetric stretching vibrational frequencies of methane in structure H and I clathrate hydrates.

Large molecules such as 2-methylbutane (CH) or 2,2-dimethylbutane (CH) form structure H (sH) hydrates with methane (CH) as a help gas. In this study, the Raman spectra of the C-H symmetric stretch region of CH enclathrated within various sH hydrates and structure I CH hydrates were analyzed in the temperature range 83-183 K. Thermal expansions of these sH hydrate samples were also measured using powder X-ray diffraction.