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Title: Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates

Abstract

Replacement of methane with carbon dioxide in hydrate has been proposed as a strategy for geologic sequestration of carbon dioxide (CO{sub 2}) and/or production of methane (CH{sub 4}) from natural hydrate deposits. This replacement strategy requires a better understanding of the thermodynamic characteristics of binary mixtures of CH{sub 4} and CO{sub 2} hydrate (CH{sub 4}-CO{sub 2} mixed hydrates), as well as thermophysical property changes during gas exchange. This study explores the thermal dissociation behavior and dissociation enthalpies of CH{sub 4}-CO{sub 2} mixed hydrates. We prepared CH{sub 4}-CO{sub 2} mixed hydrate samples from two different, well-defined gas mixtures. During thermal dissociation of a CH{sub 4}-CO{sub 2} mixed hydrate sample, gas samples from the head space were periodically collected and analyzed using gas chromatography. The changes in CH{sub 4}-CO{sub 2} compositions in both the vapor phase and hydrate phase during dissociation were estimated based on the gas chromatography measurements. It was found that the CO{sub 2} concentration in the vapor phase became richer during dissociation because the initial hydrate composition contained relatively more CO{sub 2} than the vapor phase. The composition change in the vapor phase during hydrate dissociation affected the dissociation pressure and temperature; the richer CO{sub 2} in the vapormore » phase led to a lower dissociation pressure. Furthermore, the increase in CO{sub 2} concentration in the vapor phase enriched the hydrate in CO{sub 2}. The dissociation enthalpy of the CH{sub 4}-CO{sub 2} mixed hydrate was computed by fitting the Clausius-Clapeyron equation to the pressure-temperature (PT) trace of a dissociation test. It was observed that the dissociation enthalpy of the CH{sub 4}-CO{sub 2} mixed hydrate lays between the limiting values of pure CH{sub 4} hydrate and CO{sub 2} hydrate, increasing with the CO{sub 2} fraction in the hydrate phase.« less

Authors:
; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
Earth Sciences Division
OSTI Identifier:
1048280
Report Number(s):
LBNL-4939E
Journal ID: ISSN 1520-6106; TRN: US201216%%859
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B
Additional Journal Information:
Journal Volume: 115; Journal Issue: 25; Related Information: Journal Publication Date: 2011; Journal ID: ISSN 1520-6106
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; 54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; BINARY MIXTURES; CARBON DIOXIDE; DISSOCIATION; ENTHALPY; GAS CHROMATOGRAPHY; HYDRATES; LIMITING VALUES; METHANE; MIXTURES; PRODUCTION; THERMODYNAMICS

Citation Formats

Kwon, T H, Kneafsey, T J, and Rees, E V.L. Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates. United States: N. p., 2011. Web. doi:10.1021/jp111490w.
Kwon, T H, Kneafsey, T J, & Rees, E V.L. Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates. United States. doi:10.1021/jp111490w.
Kwon, T H, Kneafsey, T J, and Rees, E V.L. Tue . "Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates". United States. doi:10.1021/jp111490w. https://www.osti.gov/servlets/purl/1048280.
@article{osti_1048280,
title = {Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates},
author = {Kwon, T H and Kneafsey, T J and Rees, E V.L.},
abstractNote = {Replacement of methane with carbon dioxide in hydrate has been proposed as a strategy for geologic sequestration of carbon dioxide (CO{sub 2}) and/or production of methane (CH{sub 4}) from natural hydrate deposits. This replacement strategy requires a better understanding of the thermodynamic characteristics of binary mixtures of CH{sub 4} and CO{sub 2} hydrate (CH{sub 4}-CO{sub 2} mixed hydrates), as well as thermophysical property changes during gas exchange. This study explores the thermal dissociation behavior and dissociation enthalpies of CH{sub 4}-CO{sub 2} mixed hydrates. We prepared CH{sub 4}-CO{sub 2} mixed hydrate samples from two different, well-defined gas mixtures. During thermal dissociation of a CH{sub 4}-CO{sub 2} mixed hydrate sample, gas samples from the head space were periodically collected and analyzed using gas chromatography. The changes in CH{sub 4}-CO{sub 2} compositions in both the vapor phase and hydrate phase during dissociation were estimated based on the gas chromatography measurements. It was found that the CO{sub 2} concentration in the vapor phase became richer during dissociation because the initial hydrate composition contained relatively more CO{sub 2} than the vapor phase. The composition change in the vapor phase during hydrate dissociation affected the dissociation pressure and temperature; the richer CO{sub 2} in the vapor phase led to a lower dissociation pressure. Furthermore, the increase in CO{sub 2} concentration in the vapor phase enriched the hydrate in CO{sub 2}. The dissociation enthalpy of the CH{sub 4}-CO{sub 2} mixed hydrate was computed by fitting the Clausius-Clapeyron equation to the pressure-temperature (PT) trace of a dissociation test. It was observed that the dissociation enthalpy of the CH{sub 4}-CO{sub 2} mixed hydrate lays between the limiting values of pure CH{sub 4} hydrate and CO{sub 2} hydrate, increasing with the CO{sub 2} fraction in the hydrate phase.},
doi = {10.1021/jp111490w},
journal = {Journal of Physical Chemistry B},
issn = {1520-6106},
number = 25,
volume = 115,
place = {United States},
year = {2011},
month = {2}
}