Guest molecule dynamics and guest-specific degassing phenomenon of binary gas hydrate investigated by terahertz time-domain spectroscopy

Abstract

Guest molecule dynamics and guest-specific degassing phenomenon of binary gas hydrate investigated by terahertz time-domain spectroscopy3

Optical Interpretation of the Chemical Process of CH4–CO2 Exchange and Its Application to Gas Hydrate Production

“…The state of the sample at 263 K should be hexagonal ice because there is no known measurable intermediate or activated states during the dissociation process from hydrate to ice or water. We previously reported that the presence of CH 4 , H 2 , and O 2 molecules in the THF sII hydrate did not affect the THz electric fields in the time domain . The notable change in the electric fields indicates that THz light is transmitted faster through ice than through the hydrate, and thus ice has a smaller refractive index than gas hydrates.…”

“…Different combinations of the guest molecules of CH 4 and CO 2 will then have a superimposed effect on the THz absorption. Considering the changes in the amplitude spectra observed for sII hydrates with different guest molecules, the guest contribution in THz-TDS may be emphasized . Although free molecules of both methane and carbon dioxide do not have a permanent dipole moment, it was recently revealed that methane showed faint absorption in the THz region due to centrifugal distortion effects .…”

“…Thus far, few studies have successfully reported the characteristics of gas hydrates in the THz range. Takeya et al studied the optical properties of structure II (sII) hydrates with different guests and compared the results with those of ice. − Koh et al recently studied the formation and degassing process of THF hydrates (sII hydrates) with temperature change by THz spectroscopy . We previously reported on the different optical properties of semiclathrate hydrates in the terahertz region and analyzed the hydrate formation in hydrate inhibitor added systems. , …”

Terahertz characterization of propane hydrate

“…36) Although several studies of ice based on THz technology have been reported, 13,14,37,38) there are few studies based on gas hydrates in the THz regime. 29,30,39) Investigating the optical and dielectric properties of gas hydrates at THz frequencies should provide useful information. In this paper, we report the modeling of dielectric parameters of gas hydrate including non-polar guest molecule.…”

Optical Properties of Tetrahydrofuran Clathrate Hydrates with Polyvinylpyrrolidone (THF + H2O + PVP) Revealed by Terahertz (THz) Time-Domain Spectroscopy

“…Moreover, terahertz (THz) spectroscopy has a function such that it is highly sensitive to hydrogen-bonded functional groups and can more favorably be used to probe the dynamics of water molecules comprising the cage frameworks in clathrate hydrates. Takeya et al measured the optical properties of ice, THF hydrate, propane hydrate, and SF 6 hydrate in the THz region. − Additionally, in our previous works, we explored the guest dynamics of gaseous guest molecules and the physical properties of semiclathrate hydrates using THz-time-domain spectroscopy (TDS) . In this study, we attempted to use THz-TDS to closely examine the formation behavior of tetrahydrofuran (THF) hydrate in KHI-dosed PVP.…”