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

Abstract

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 265–273K and pressures of 4–10MPa. Adsorption rates of H2-furan and H2-6.8mol% 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, ΔEDa, for H2 diffusion into clathrate hydrates calculated from the Arrhenius plots depended on the hydrate guest additive and were determined to be: 18.0kJ/mol (6.2mol% THF), 30.7kJ/mol (5.6mol% THF), and 100kJ/mol (cyclopentane). Based on the ΔEDa 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.