| Summary: | Understandingthe phase behavior and stability of nanoconfined natural gas hydrates is of great importance not only for fundamental clathrate research but also for practical applications of gas hydrates. In this study, we synthesized methane hydrate within a layered double hydroxide (LDH) powder sample. X-ray diffraction (XRD) analysis demonstrated that structure I (sI)-type methane clathrate hydrate was formed in the non-interlamellar voids of the LDH. Both the measured P – T equilibrium curves and atomistic molecular dynamics (MD) simulations showed that the confined clathrate hydrate had lower stability and more severe formation conditions (lower melting temperature at the same pressure) than its bulk form. Furthermore, Raman spectra showed that the confined hydrate had significantly lower methane occupancy in its large 5 12 6 2 cages. In conclusion, nanoconfinement and a high surface charge density strongly inhibit the phase behavior of methane hydrates formed in LDH. These results provide important information for potential applications of nanoconfined methane hydrates, such as gas storage, as well as for the exploitation of gas hydrates in sediments.
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