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Title: Neutron diffraction studies of CO{sub 2} clathrate hydrate: Formation from deuterated ice

Abstract

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) structuremore » analysis from powder diffraction data without the presence of solid CO{sub 2}.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Argonne National Lab., IL (US)
Sponsoring Org.:
USDOE
OSTI Identifier:
20075891
DOE Contract Number:  
W-31109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory
Additional Journal Information:
Journal Volume: 104; Journal Issue: 21; Other Information: PBD: 1 Jun 2000; Journal ID: ISSN 1089-5639
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBON DIOXIDE; NEUTRON DIFFRACTION; CLATHRATES; HYDRATES; ICE; HEAVY WATER; SYNTHESIS

Citation Formats

Henning, R.W., Schultz, A.J., Thieu, V., and Halpern, Y. Neutron diffraction studies of CO{sub 2} clathrate hydrate: Formation from deuterated ice. United States: N. p., 2000. Web. doi:10.1021/jp0001642.
Henning, R.W., Schultz, A.J., Thieu, V., & Halpern, Y. Neutron diffraction studies of CO{sub 2} clathrate hydrate: Formation from deuterated ice. United States. doi:10.1021/jp0001642.
Henning, R.W., Schultz, A.J., Thieu, V., and Halpern, Y. Thu . "Neutron diffraction studies of CO{sub 2} clathrate hydrate: Formation from deuterated ice". United States. doi:10.1021/jp0001642.
@article{osti_20075891,
title = {Neutron diffraction studies of CO{sub 2} clathrate hydrate: Formation from deuterated ice},
author = {Henning, R.W. and Schultz, A.J. and Thieu, V. and Halpern, Y.},
abstractNote = {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}.},
doi = {10.1021/jp0001642},
journal = {Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory},
issn = {1089-5639},
number = 21,
volume = 104,
place = {United States},
year = {2000},
month = {6}
}