Clathrate hydrate, also known as gas hydrates are crystalline inclusion structures formed from the hydrogen bonding of water molecules arranged to form cavities that enclose small molecules, such as CH4 or CO2. Natural gas hydrates are abundant on the ocean floor or in the permafrost constitute an untapped source of hydrocarbons that exceeds all other known sources of hydrocarbons combined today. They have also been considered as possible sources of global climate change; i.e., methane wetland emissions and permafrost thawing may significantly affect the climate system. The fact that the gas molecules forms a hydrate has been known for many years and numerous researches has achieved on the nucleation thermodynamics and kinetics, however there is still a lack of information on how gas hydrates behave and reside during the dissociation phase. In-situ wide-angle x-ray scattering (WAXS) measurements were performed on laboratory-made CH4 and CO2 hydrate samples under ambient pressure up to 260 k. Synchrotron high energy X-ray has shown an advantage for studying fast kinetics. The lattice constant and thermal expansivity of both hydrates were also obtained by sequential Rietveld refinement. The results allow for checking of previous assumptions and parameters obtained from molecular dynamics simulations or lattice dynamical calculations and may lead to better understandings of gas hydrates.

New insights into dissociation behavior of methane and carbon dioxide hydrates at ambient pressure by in situ wide-angle x-ray scattering

255th National Meeting (2018)

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