Raman spectroscopic study of CO 2 in hydrate cages

Spectroscopic and thermodynamic investigations of clathrate hydrates of methacrolein

“…3) were also observed at around 1274 and 1380 cm À1 for the vibrational frequencies of CO 2 . 26 Chen et al investigated the vibrational frequencies of CO 2 in the small and large cages of sI or sII hydrates, and their ndings are in good agreement with our results. 26 At this stage, the identication of gaseous guest molecules in the small cages of sII hydrates has been successfully demonstrated, but the types of methacrolein conformers in the large cages of sII hydrates remain unknown.…”

Anharmonicity and Fermi resonance in the vibrational spectra of a CO2 molecule and CO2 molecular crystal: Similarity and distinctions

“…The fundamental vibration band is not shown in this figure because it does not influence the shape of TPS band at Γ = 0. The anharmonicity constant of the fourth order is negative A p ≤ 0; therefore, TPS shifts to the low energy range, and the broad band of TPS is deformed in accordance with Equation . When the value A p is small, the two‐phonon band is rather wide and has two maxima of almost equal intensities on both sides (Curve 1), which reflects the density of states distribution within this two‐phonon band at one‐dimensional dispersion law.…”

Isostructural and cage-specific replacement occurring in sII hydrate with external CO2/N2 gas and its implications for natural gas production and CO2 storage

“…4. The occupation of both CO 2 and N 2 molecules in the cages of sII hydrate was clearly confirmed (Table 1), but an accurate cage designation for CO 2 and N 2 was not made because CO 2 and N 2 generally do not show oneto-one correspondence between Raman shifts and hydrate cages [1,27]. However, it is reasonably expected that during the replacement, CO 2 molecules favorably attack C 3 H 8 molecules trapped in the large cages whereas N 2 molecules mainly attack CH 4 molecules captured in the small cages, considering the molecular size of the guest molecules and the dimensions of each cage.…”