PHASE BEHAVIOR OF LOW-PRESSURE HYDROGEN CLATHRATE HYDRATE

L.J. ROVETTO; J. SCHOONMAN; C.J. PETERS

Trondheim, Noruega

Conferencia; 5th International Conference on Gas Hydrates; 2005

ABSTACT For a number of reasons, it is expected that in the near future hydrogen will be the main source of fuel in the automotive sector. One of the reasons is that its chemical energy is at least three times higher than alternative chemical fuels. Although, hydrogen is abundantly available and environmentally benign, storage of hydrogen at acceptably favorable conditions and with high energy density is still an unresolved problem. Recently, the gas clathrate hydrate of hydrogen has been discovered, and it turned out that the applied pressure to stabilize the material was extremely high, i.e., at temperatures below ambient the equilibrium pressure of the hydrogen hydrate is as high as 230 MPa. However, application of so-called gas hydrate promoters, it turned out to be possible to have hydrogen clathrate hydrate stable at pressures below 10 MPa. This finding has been recognized as a candidate solution for hydrogen storage. The accepted idea of single occupancy of the cavities in the gas hydrate structure does no apply for small molecules as Ar, N2, etc., and for hydrogen clathrate hydrate double and even quadruple occupancy has been established, which means that the energy density of hydrogen clathrate hydrate is relatively high. In this contribution experimental results are reported on the phase behavior of hydrogen clathrate hydrate in presence of certain selected promoters. The stability conditions for the hydrate phase were measured within a temperature range of 271-282 K and pressures up to 14.5 MPa were applied. The maximum promoting effect was found at concentrations of THF around 5-6 mole %.