Hydrogen Storage in Semiclathrate Hydrates of Tetrabutyl Ammonium Chloride and Tetrabutyl Phosphonium Bromide

Original calorimetric and phase equilibrium properties for hydrogen + tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride (TBACl), or tetrabutylphosphonium bromide (TBPB) semiclathrate hydrates were measured using differential scanning calorimetry under pressure. The dissociation temperatures of H2 + TBACl and H2 + TBPB semiclathrate hydrates are very close to the ambient temperature at low pressures around 15.0 MPa. H2 + TBACl and H2 + TBPB systems therefore exhibit better and comparable stability than the H2 + TBAB system at equivalent pressure, respectively. The amount of hydrogen stored in H2 + TBACl and H2 + TBPB semiclathrate hydrates was estimated in terms of the H2-to-water mole ratio (n H2 /n H2O) calculated from disssociation enthalpies and (p, T) equilibrium data. In terms of mass fraction deduced from the ratio (n H2 /n H2O), H2 + TBACl and H2 + TBPB semiclathrate hydrates can store 0.12 % and 0.14 % of hydrogen, respectively. Moreover, the quantity of hydrogen stored in these two semiclathrate hydrates is significantly higher than that stored in the H2 + TBAB system.