(165d) Hydrogen Storage through Clathrate Hydrate Formation in Porous Media

Clathrate hydrate is a typical solid inclusion compound that was formed between ice crystals and light molecular weight gases at elevated pressures and low temperatures. Though the hydrogen uptake of pure hydrogen clathrate is higher than binary clathrate hydrate with a water-tetetrahydrofuran (H2O/THF) mixture, the binary clatharate is probably more interesting and important because the binary clathrate hydrate can be formed at much less extreme conditions than the pure clathrates. In the first phase of this work, ordered mesoporous carbon (OMC) was doped with a H2O/THF mixture of variable loadings, followed by hydrogen adsorption measurement at 270K and hydrogen pressures up to 163 bar. The OMC adsorbents doped with 0.75 wt% and 0.5 wt% of the H2O/THF mixture showed a higher hydrogen uptake than the pure OMC due to the combined effect of physical adsorption and H2O/THF/H2 clathrate formation.

The second phase of the work is aimed at reducing the formation time of the binary clathrates. It was speculated that smaller clathrate hydrate particles have faster formation kinetics. To evaluate this hypothesis, we doped the THF/H2O mixture on four porous media with variable pore sizes between 49Å and 225Å, and then studied the hydrogen storage kinetics in these adsorbents. It was observed that by adopting this unique technique, the clathrate formation time was reduced to 27 minutes as compared to 10 hours to 6 days of formation time reported in the literatures. A kinetic model was applied to estimate the diffusivity of hydrogen in the clathrate crystals.