Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy
The pressure-induced amorphization (PIA) of ice and clathrate hydrates occurs at temperatures significantly below their melting and decomposition points. The PIA of type I clathrate hydrates containing methane and ethane as guest molecules was investigated using Raman and infrared (IR) spectroscopy....
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The Royal Society of Chemistry
2023
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fttokushimauniv:oai:lib.tokushima-u.ac.jp:repository/118577 2024-02-11T10:05:49+01:00 Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy Noguchi, Naoki Shiraishi, Yui Kageyama, Maho Yokoi, Yuu Kurohama, Saki Okada, Natsuki Okamura, Hidekazu 2023-10-11 http://repo.lib.tokushima-u.ac.jp/118577 eng eng The Royal Society of Chemistry 14639076 14639084 AA11301773 AA11723355 http://repo.lib.tokushima-u.ac.jp/118577 Journal Article 2023 fttokushimauniv 2024-01-17T18:24:29Z The pressure-induced amorphization (PIA) of ice and clathrate hydrates occurs at temperatures significantly below their melting and decomposition points. The PIA of type I clathrate hydrates containing methane and ethane as guest molecules was investigated using Raman and infrared (IR) spectroscopy. With isothermal compression at 100 K, methane hydrate (MH) underwent PIA at 2–3.5 GPa, whereas ethane hydrate (EH) underwent PIA at 4.0–5.5 GPa. The type I clathrate structure consists of small (512) and large (51262) cages. The Raman results revealed that the collapsed small and large cages in the amorphous forms of MH and EH were not distinguishable. The collapsed cages, including the methane and ethane molecules, were similar to the small and large cages, respectively. Their water networks were folded or expanded during the PIA process so that the cavity sizes of the collapsed cages were compatible with those of the guest molecules. Peaks in the IR spectra of crystalline MH assignable to the ro-vibrational transition of methane in large cages were observed in the C–H stretching wavenumber region below 40 K. The ro-vibrational IR band disappeared after amorphization, suggesting that the rotational motion of the methane molecule in the large cage was frozen by the collapse, as reported in previous dielectric spectroscopic and simulation studies. This study contributes to a better understanding of the changes in the local structure around guest molecules during PIA and the dynamics of the guest molecules. Article in Journal/Newspaper Methane hydrate Tokushima University Institutional Repository |
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Tokushima University Institutional Repository |
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language |
English |
description |
The pressure-induced amorphization (PIA) of ice and clathrate hydrates occurs at temperatures significantly below their melting and decomposition points. The PIA of type I clathrate hydrates containing methane and ethane as guest molecules was investigated using Raman and infrared (IR) spectroscopy. With isothermal compression at 100 K, methane hydrate (MH) underwent PIA at 2–3.5 GPa, whereas ethane hydrate (EH) underwent PIA at 4.0–5.5 GPa. The type I clathrate structure consists of small (512) and large (51262) cages. The Raman results revealed that the collapsed small and large cages in the amorphous forms of MH and EH were not distinguishable. The collapsed cages, including the methane and ethane molecules, were similar to the small and large cages, respectively. Their water networks were folded or expanded during the PIA process so that the cavity sizes of the collapsed cages were compatible with those of the guest molecules. Peaks in the IR spectra of crystalline MH assignable to the ro-vibrational transition of methane in large cages were observed in the C–H stretching wavenumber region below 40 K. The ro-vibrational IR band disappeared after amorphization, suggesting that the rotational motion of the methane molecule in the large cage was frozen by the collapse, as reported in previous dielectric spectroscopic and simulation studies. This study contributes to a better understanding of the changes in the local structure around guest molecules during PIA and the dynamics of the guest molecules. |
format |
Article in Journal/Newspaper |
author |
Noguchi, Naoki Shiraishi, Yui Kageyama, Maho Yokoi, Yuu Kurohama, Saki Okada, Natsuki Okamura, Hidekazu |
spellingShingle |
Noguchi, Naoki Shiraishi, Yui Kageyama, Maho Yokoi, Yuu Kurohama, Saki Okada, Natsuki Okamura, Hidekazu Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy |
author_facet |
Noguchi, Naoki Shiraishi, Yui Kageyama, Maho Yokoi, Yuu Kurohama, Saki Okada, Natsuki Okamura, Hidekazu |
author_sort |
Noguchi, Naoki |
title |
Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy |
title_short |
Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy |
title_full |
Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy |
title_fullStr |
Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy |
title_full_unstemmed |
Direct observation of pressure-induced amorphization of methane/ethane hydrates using Raman and infrared spectroscopy |
title_sort |
direct observation of pressure-induced amorphization of methane/ethane hydrates using raman and infrared spectroscopy |
publisher |
The Royal Society of Chemistry |
publishDate |
2023 |
url |
http://repo.lib.tokushima-u.ac.jp/118577 |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_relation |
14639076 14639084 AA11301773 AA11723355 http://repo.lib.tokushima-u.ac.jp/118577 |
_version_ |
1790603014465126400 |