Local structure analysis of low-temperature neutron pair distribution function coupled with molecular dynamics simulations of CH 4 and CO 2 hydrates from 2 to 210 K

Cladek, Bernadette R.; Everett, S. Michelle; McDonnell, Marshall T.; Kizzire, Dayton G.; Tucker, Matthew G.; Keffer, David J.; Rawn, Claudia J.

doi:10.1016/j.fuel.2021.120908

DOE OSTI · 1814260

Local structure analysis of low-temperature neutron pair distribution function coupled with molecular dynamics simulations of CH 4 and CO 2 hydrates from 2 to 210 K

Cladek, Bernadette R.·Everett, S. Michelle·McDonnell, Marshall T.·Kizzire, Dayton G.·Tucker, Matthew G.·Keffer, David J.·Rawn, Claudia J.

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Abstract

CH 4 hydrates occur naturally and are an abundant potential fuel source with a corresponding risk of potent greenhouse gas release, due to their stability conditions at low temperature and high pressure. Byproduct CO 2 can be exchanged with CH 4 in these natural deposits and can potentially stabilize the hydrates at higher temperatures. CH 4 , CO 2 , and mixed CH 4 -CO 2 hydrates are studied with in situ neutron pair distribution function experiments from 2 to 210 K to investigate the impact of varying the CH 4 -CO 2 guest composition in the gas hydrate structure. These experiments combined with Reverse Monte Carlo analysis allow for the characterization of intermolecular CH 4 and CO 2 interactions with the water molecules which form the hydrate lattice and how they impact the local structure of the lattice itself. Results indicate that when CH 4 and CO 2 co-occupy the hydrate, the host is more strongly distorted than in the pure CH 4 and CO 2 hydrates, but this becomes less defined with increasing temperature. The presence of CO 2 in mixed hydrate increases the stability range and creates a barrier for CH 4 to completely leave the structure.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY Crystallography Methane hydrate Mixed methane-carbon dioxide hydrates Molecular dynamics simulation Neutron diffraction Reverse Monte Carlo simulation

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Cladek, Bernadette R., Everett, S. Michelle, McDonnell, Marshall T., Kizzire, Dayton G., Tucker, Matthew G., Keffer, David J., Rawn, Claudia J.. 2021-04-30. Local structure analysis of low-temperature neutron pair distribution function coupled with molecular dynamics simulations of CH 4 and CO 2 hydrates from 2 to 210 K. https://doi.org/10.1016/j.fuel.2021.120908

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