Noble gases, such as xenon (Xe) and
krypton (Kr), can be captured
in hydrate cages, and thus, gas hydrates can be used as capture and
storage media for these gases. This study examined the phase equilibria,
crystal structure, and guest distributions of Xe and Kr hydrates in
the presence of tetrahydrofuran (THF). The three-phase [hydrate (H)–liquid
(L)–vapor (V)] equilibria of the Xe + THF + water and Kr +
THF + water systems were measured at two different concentrations
of THF (1.0 and 5.6 mol %) to examine the thermodynamic promotion
effect of THF on Xe and Kr hydrates. The inclusion of THF in the hydrate
cages led to significant shifts in the equilibrium curves of the Xe
and Kr hydrates to lower pressure and higher temperature regions.
The powder X-ray diffraction patterns and the 129Xe and 13C nuclear magnetic resonance spectra revealed that THF was
enclathrated in the large (51264) cages of structure
II hydrates and that the small (512) cages were occupied
by Xe (or Kr). In particular, at 1.0 mol % THF, the large 51264 cages were partly occupied by Xe (or Kr) as a result
of tuning behavior. The experimental results expand the basic understanding
of hydrate-based gas capture and storage for Xe and Kr.
Tetra-n-butyl ammonium chloride (TBAC) is a semi-clathrate former that can be used for clathrate-based gas capture and storage since TBAC semi-clathrate has vacant small cages available for entrapping gas molecules...
In this study, a new sI–sII dual hydrate former [chlorodifluoromethane (CHClF2); an important greenhouse gas with a global warming potential of 1,810], which forms sI hydrate by itself and forms...
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