Neutron diffraction studies of CO{sub 2} clathrate hydrate: Formation from deuterated ice
The formation of CO{sub 2} clathrate hydrate was investigated by using time-of-flight neutron powder diffraction at temperatures ranging from 230 to 290 K with a CO{sub 2} gas pressure of 900 psi. CO{sub 2} clathrate hydrate was prepared in situ from deuterated ice crystals at 230, 243, 253, and 263 K by pressurizing the system with CO{sub 2} gas to produce the hydrate in approximately 70% yield. Nearly complete conversion from the hexagonal ice to the sI type CO{sub 2} hydrate was observed as the temperature of the sample was slowly increased through the melting point of D{sub 2}O ice. The conversion of ice into hydrate is believed to be a two-stage process in which an initial fast conversion rate is followed by a slower, diffusion-limited rate. On the basis of a shrinking core diffusion model, an activation energy of 6.5 kcal/mol was obtained from the temperature dependence of the reaction. The findings suggest that the formation of the hydrate is through a reaction between CO{sub 2} and water molecules in the quasi-liquid layer (QLL). The CO{sub 2} hydrate remained stable following removal of excess liquid CO{sub 2} and subsequent pressurization with helium, allowing for a low-temperature (14 K) structure analysis from powder diffraction data without the presence of solid CO{sub 2}.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 20075891
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 21 Vol. 104; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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