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Title: Insights into the structure of mixed CO2/CH4 in gas hydrates

The exchange of carbon dioxide for methane in natural gas hydrates is an attractive approach to harvesting CH4 for energy production while simultaneously sequestering CO2. In addition to the energy and environmental implications, the solid solution of clathrate hydrate (CH4)1-x(CO2)x·5.75H2O provides a model system to study how the distinct bonding and shapes of CH4 and CO2 influence the structure and properties of the compound. In this paper, high-resolution neutron diffraction was used to examine mixed CO2/CH4 gas hydrates. CO2-rich hydrates had smaller lattice parameters, which were attributed to the higher affinity of the CO2 molecule interacting with H2O molecules that form the surrounding cages, and resulted in a reduction in the unit-cell volume. Experimental nuclear scattering densities illustrate how the cage occupants and energy landscape change with composition. Finally, these results provide important insights on the impact and mechanisms for the structure of mixed CH4/CO2 gas hydrate.
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [5]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering
  2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemistry and Engineering Materials Division
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
Publication Date:
OSTI Identifier:
1185328
Grant/Contract Number:
AC05-00OR22725; DGE0801470
Type:
Accepted Manuscript
Journal Name:
American Mineralogist
Additional Journal Information:
Journal Volume: 100; Journal Issue: 5-6; Journal ID: ISSN 0003-004X
Publisher:
Mineralogical Society of America
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF), Washington, DC (United States); USDOE Office of Fossil Energy (FE)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES neutron diffraction; methane hydrate; carbon dioxide/methane exchange; Fourier density maps