Prediction of hydrogen hydrates equilibria under an organic compound

Because of excellent storage capacity, H₂ hydrates can be used as a storage medium to secure the supply of H₂. An excess Gibbs energy model for low-pressure H₂ hydrates under a tetrahydrofuran (THF) aqueous solution was proposed. THF entered only the large cavities of Structure-II clathrates while H₂ could enter both small and large cavities with the occupancies of 2 and 4, respectively. The 2H2/4H2 molecules in the cavities were treated as rigid body clusters and the corresponding intermolecular potential parameters between water and H₂ clusters were used to calculate the Langmuir constants of H₂ clusters in the cavities. The excess Gibbs energy model along with the Lee-Holder cell distortion model and the vander Waals-Platteeuw statistical thermodynamic model was used to predict the dissociation pressures of H₂-THF double hydrates. There was a good agreement between the predicted dissociation pressures and the experimental dissociation pressures. The proposed model was extended to the gas hydrates formed from the mixtures containing H₂, THF, and other gases. This is an abstract of a paper presented at the 2006 AIChE National Meeting (San Francisco, CA 11/12-17/2006).