Large-Cage Occupancies of Hydrogen in Binary Clathrate Hydrates Dependent on Pressures and Guest Concentrations

• Published in: Journal of physical chemistry. C 2010-09, Vol.114 (35), p.15218-15222
• Main Authors: Sugahara, Takeshi, Haag, Joanna C, Warntjes, Ashleigh A, Prasad, Pinnelli S. R, Sloan, E. Dendy, Koh, Carolyn A, Sum, Amadeu K
• Format: Article
• Language: English
• Subjects: C: Energy Conversion and Storage
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp105379x

Balancing the formation and storage pressure with the storage capacity is one of the most significant steps toward developing H2 storage in hydrates. The large-cage occupancies of hydrogen molecules in tetrahydrofuran (THF), acetone, cyclohexanone (CHONE), and methylcyclohexane (MCH) hydrates were investigated by Raman spectroscopy, volumetric gas release measurement, and X-ray diffraction analysis in a pressure region below the equilibrium pressure of pure H2 hydrates at 255 ± 2 K. The results from the measurements show that H2 molecules occupy the large cage of the structure II THF+H2, acetone+H2, and CHONE+H2 hydrates at the suitable pressures and concentrations of promoter guest species, while H2 molecules do not occupy the largest cage of the structure H MCH+H2 hydrates, even around 70 MPa. The present work reveals that the large-cage occupancy of H2 strongly depends on the pressure and the concentration of promoter guest species. The maximum storage amount of H2 in the acetone+H2 hydrate was 3.6 ± 0.1 wt %, similar to that of THF+H2 hydrate, at 74 MPa and 255 ± 2 K. Acetone is superior to THF and CHONE as the promoter based on the relation between pressure and the large-cage occupancy of H2 molecules.