Multiple adsorption resistance model for constituent molecular effects in hydrogen clathration kinetics in clathrate hydrate particles

• Properties reported on clathrate hydrates with guest additives for H2 storage.
• Guest additives: THF, THF-d8, furan, cyclopentane and tetrahydrothiophene.
• Three resistance model: hydrate framework, guest inclusion cage, and H2 adsorbed shell.
• Non-included guest additives affect H2 diffusion pathway.
• S-cage distortion affects H2 adsorption rate.

Adsorption rates are reported for H2-tetrahydrofuran (THF), H2-THF (D2O), H2-THF-d8, H2-furan, H2-cyclopentane (CP) and H2-tetrahydrothiophene (THT) binary clathrate hydrates at temperatures of 265–273 K and pressures of 4–10 MPa. Adsorption rates of H2-furan and H2-6.8 mol% THF binary clathrate hydrates were the fastest among these binary clathrate hydrates. The lattice constant of hydrates were determined to analyze the adsorption data with a newly proposed multiple adsorption resistance (MAR) model. The effect of the non-included additive guest molecule on hydrogen adsorption rate was important because they promoted formation of pores and grain boundaries when hydrate particles formed. Activation energies, ΔEDaΔEDa, for H2 diffusion into clathrate hydrates calculated from the Arrhenius plots depended on the hydrate guest additive and were determined to be: 18.0 kJ/mol (6.2 mol% THF), 30.7 kJ/mol (5.6 mol% THF), and 100 kJ/mol (cyclopentane). Based on the ΔEDaΔEDa values, H2 diffusion pathway in hydrate particles depends on the clathrate hydrate formation process and the interactions between guest additive molecule and the host molecule.

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