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Issue 44, 2011
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Clathrate hydrate formation after CO2–H2O vapour deposition

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Abstract

We study vapour condensation of carbon dioxide and water at 77 K in a high-vacuum apparatus, transfer the sample to a piston-cylinder apparatus kept at 77 K and subsequently heat it at 20 MPa to 200 K. Samples are monitored by in situ volumetric experiments and after quench-recovery to 77 K and 1 bar by powder X-ray diffraction. At 77 K a heterogeneous mixture of amorphous solid water (ASW) and crystalline carbon dioxide is produced, both by co-deposition and sequential deposition of CO2 and H2O. This heterogeneous mixture transforms to a mixture of cubic structure I carbon dioxide clathrate and crystalline carbon dioxide in the temperature range 160–200 K at 20 MPa. However, no crystalline ice is detected. This is, to the best of our knowledge, the first report of CO2 clathrate hydrate formation from co-deposits of ASW and CO2. The presence of external CO2 vapour pressure in the annealing stage is not necessary for clathrate formation. The solid–solid transformation is accompanied by a density increase. Desorption of crystalline CO2 atop the ASW sample is inhibited by applying 20 MPa in a piston-cylinder apparatus, and ultimately the clathrate is stabilized inside layers of crystalline CO2 rather than in cubic or hexagonal ice. The vapour pressure of carbon dioxide needed for clathrate hydrate formation is lower by a few orders of magnitude compared to other known routes of CO2 clathrate formation. The route described here is, thus, of relevance for understanding formation of CO2 clathrate hydrates in astrophysical environments.

Graphical abstract: Clathrate hydrate formation after CO2–H2O vapour deposition

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Publication details

The article was received on 08 Jun 2011, accepted on 08 Sep 2011 and first published on 26 Sep 2011


Article type: Paper
DOI: 10.1039/C1CP21856E
Phys. Chem. Chem. Phys., 2011,13, 19765-19772

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    Clathrate hydrate formation after CO2–H2O vapour deposition

    C. Mitterdorfer, M. Bauer and T. Loerting, Phys. Chem. Chem. Phys., 2011, 13, 19765
    DOI: 10.1039/C1CP21856E

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