Hydrogen-rich natural gas hydrates formation kinetics in the presence of promoters

Commercial exploitation of hydrogen-rich natural gas (CH4/C2H6/H-2, HRNG) requires the development of a technology platform for safe and economical gas transportation and storage. Recent discoveries confirm that HRNG gas mixtures can be stored in HRNG hydrates under moderate pressure and temperature conditions. Here, we demonstrate enhanced uptake of HRNG gas mixture in clathrate hydrate catalysts by two different classes of promoters in three different configurations for different H-2 mol% (33%-80%) in the HRNG feed gas. The experimental study confirmed the positive effect of promoters on HRNG hydrate formation kinetics and further indicates that promoter selection should be based on H-2 mol% in the HRNG mixture. The experimental observations showed that the kinetic promoters (KP) were effective at low H-2 concentration (33 mol%), while the thermodynamic promoters (TP) were effective at high H-2 concentration (70-80 mol%) in the HRNG mixture. This difference in formation kinetics (in the presence of promoters) suggests that the CH4/C2H6 mixture controls formation kinetics and crystal structure, H-2 mol% affects H-2 cage occupancy, and overall uptake in hydrates is influenced by competition between liquid and gaseous TP. In addition, the authors commented on current research gaps and provided the reader with directions for future research. The results of this work will contribute to the further development of HRNG hydrate synthesis via various routes, such as novel promoters.