Reverse micelles enhance the formation of clathrate hydrates of hydrogen.

Hypothesis: Clathrate hydrates of hydrogen form at relatively low pressures (e.g., ca. 10 MPa) when a co-former compound is added. In that case, however, the gravimetric amount of stored hydrogen drops to less than 1 wt% from ca. 5.6 wt% without a co-former. Another factor hindering the entrapment of hydrogen into a clathrate matrix appears to be of a kinetic origin, in that the mass transfer of hydrogen into clathrates is limited by the macroscopic scale of the gas-water interfaces involved in their formation. Thus, the enhanced formation of binary (hydrogen + co-former) hydrates would represent a major achievement in the attempt to exploit those materials as a convenient means for storing hydrogen.

Experiments: Here, we present a simple process for the enhanced formation of binary hydrates of hydrogen and several co-formers, which is based on the use of reverse micelles for reducing the size of hydrate-forming gas-water interfaces down to tens of nanometers. This reduction of particle size allowed us to reduce the kinetic hindrance to hydrate formation.

Findings: The present process was able to (i) enhance the kinetics of the formation process; and (ii) assist clathrate formation when using water-insoluble coformers (e.g., cyclopentane, tetrahydrothiophene).