Clathrate hydrates for hydrogen storage: The impact of tetrahydrofuran, tetra-n-butylammonium bromide and cyclopentane as promoters on the macroscopic kinetics

Hydrogen hydrate formation and decomposition kinetics using tetrahydrofuran (THF), tetra-n-butylammonium bromide (TBAB) and cyclopentane (CP) as promoters under similar experimental conditions was studied. First set of experiments on hydrate formation were conducted at same promoter concentrations, experimental pressure and experimental temperature and the second set of experiments were conducted at same experimental pressure, same driving force and varying promoter concentrations. Hydrogen storage capacity of THF/Hydrogen hydrate was the highest amongst the three promoters under the experimental conditions studied. Hydrogen uptake of 0.0173 mole of gas/mole of water was obtained for the 3.5 mol% THF solution and it was about 2 times higher than hydrogen uptake obtained for 3.5 mol% TBAB solution under similar experimental conditions. With the same amount of heat supplied, TBAB/Hydrogen mixed semi-clathrates took longer time to dissociate compared to THF/Hydrogen hydrates under similar decomposition conditions. It was very difficult to form CP/Hydrogen hydrates even at a very high driving force.