2:15 PM - 2:30 PM
[MIS17-03] Effect of low concentration hydrogen sulfide on cage occupancy during hydrate formation
Keywords:gas hydrate, hydrogen sulfide, cage occupancy, Raman spectroscopy
Hydrate samples were synthesized in a pressure cell (volume: 30mL) at 273.2K and retrieved the crystals at the temperature of liquid nitrogen. Concentration of hydrogen sulfide in the hydrate-bound gas was controlled less than several percent. Hydrate-bound and residual gases were obtained and their gas compositions were determined using a gas chromatograph. Raman spectra of the crystals were obtained at 123 K in the range 2,800-3,000 cm-1 and 2,500-2,700 cm-1 for the C-H stretching peaks of methane and the S-H stretching peaks of hydrogen sulfide, respectively. The Raman peaks were fitted using a Voigt function to obtain the integrated intensities of the two peaks corresponding to methane and hydrogen sulfide encaged in the large and small cages of the cubic structure I.
The cage occupancy ratio of large to small cages for methane slightly increased with the concentration of hydrogen sulfide, whereas that for hydrogen sulfide was smaller than that for methane. These results indicate that hydrogen sulfide molecules prefer to be encaged in small cages and molecules of methane tend to encage in large cages.