Hydrogen solubility in gas hydrates with various auxiliary guests. Methane hydrate case study and comparison with the literature data

Abstract

The experimental data on hydrogen solubility in methane gas hydrate and new data on phase equilibria in the hydrogen - methane - water system are presented in this work. The solubility data were obtained for hydrogen partial pressures from 0.8 to 5.4 MPa. It was found that hydrogen solubility in methane and carbon dioxide hydrates is almost the same and the dependence of hydrogen content on hydrogen partial pressure can be fitted with the equation ln(CH2) = −4.332(54) + 0.919(62)-ln(PH2), where CH2 is the hydrogen content in the hydrate (wt%) and PH2 is the hydrogen partial pressure (MPa). The data obtained in this work were compared with available data on hydrogen solubility in sI and sII hydrates. Analysis of data on the solubility of hydrogen in sII double hydrates with different thermodynamic promoters (tetrahydrofuran, cyclopentane, propane, tetrathiophene, furan) taken from various literature sources also shows a relatively small scatter with respect to the straight line approximating them. In general, the fraction of free small 512 cages filled with hydrogen decreases in the following order: sI methane hydrate > sI CO2 hydrate > sII hydrates.