Clathrate hydrates are crystalline inclusions of gas and water (the figure, top right, shows a typical crystal structure of hydrates illustrating the cage-like structure formed by water). Hydrates form as a consequence of the tendency of water to reorient in the presence of a non-polar solute (typically light hydrocarbon gases such as methane) to maintain hydrogen bonding. They have been extensively studied for their relevance to natural gas recovery, processing, and transportation. Our research seeks to exploit hydrate formation thermodynamics and kinetics in the development of technologies for novel separations and materials synthesis, and also in new technologies for gas storage, transportation, and CO2 disposal. The research is based on the formation of hydrates in microdroplets of water stabilized by surfactants. These droplets are in a hydrocarbon solvent (water-in-oil microemulsions).

In these microemulsions, the gas-water contact area is dramatically enhanced. In oil-in-water microemulsions, the hydrate forming gas dissolves readily in the hydrocarbon solvent, and is very accessible to the water pools.

We have shown that hydrates can be induced to form from the microaqueous pools of water-in-oil microemulsions. An interesting aspect of hydrate formation in these systems, is that the hydrates nucleate and precipitate out from solution (hydrates have a higher density than the organic solvent). Thus, gas access to the water phase is maintained, and hydrates continue to form with minimal mass transfer limitations. The following are specific implications of the phenomenon.

The formation of clathrate hydrates in the microaqueous environment of water-in-oil microemulsions was pioneered in our laboratories. The concepts of rapid hydrate formation, controlling droplet size through hydrate formation, and the generation of small hydrate crystallites are consequences of this original finding. Scientifically, hydrate formation in these microdroplets is extremely interesting as it offers the opportunity to probe the fundamentals of hydrate formation. Using scattering and spectroscopy, one can probe the dynamics of hydrate formation and look at the early events of water reorientation to the hydrate structure. This is possible simply because each droplet is identical and serves as a microcompartment which can be probed. For example, our ongoing work will use small angle neutron scattering to identify incipient hydrate formation and the growth of hydrate crystals. This will lead to a better insight into the mechanisms of water rearrangement through hydrogen bonding.

BACK