Gas Hydrate Clathrates

Gas Hydrate clathrates are elevated-pressure (P) and low-temperature (T) solid phases in which gas molecule guests are physically incorporated into hydrogen-bonded cage-like water host frameworks. Clathrate hydrates are important scientifically and technologically because...

1. methane hydrates within seafloor sediments and in permafrost represent the largest terrestrial hydrocarbon resource;
2. carbon dioxide clathrates are important phases in proposals to sequester CO₂ in the deep oceans;
3. hydrogen clathrates are a potential clean fuel source with extremely high energy density;
4. clathrates (including semiclathrates) may be useful engineering materials for gas storage and separation; and
5. methane, hydrogen, and CO₂ clathrates are potentially important phases with solar system bodies (comets, Moon, Mars, satellites of gas giant planets).

Despite their engineering and scientific importance, much remains to be learned about gas-hydrate clathrates' crystal structures, bonding mechanisms, phase diagrams, thermodynamics, formation/decomposition kinetics, chemical and mechanical stability, acoustic (seismic) elasticities, reactions with sediments, diffusion/transport properties, and environmental effects under climate change. This relative lack of information exists because clathrates are only stable under high-P, low-T conditions, thereby precluding or limiting many traditional experimental methods of investigation.

LANL has been investigating gas-hydrate clathrates for several years. Work has focused on theoretical molecular dynamics studies, engineering applications to gas separations, modeling of methane hydrate extraction using pore-scale and continuum reactive transport codes, neutron diffraction studies of phase stabilities and bonding as a function of P and T, and inelastic neutron scattering studies of bonding. A full list of LANL publications is provided on the publication list.