Rietveld Analysis of Binary (2,5-Dihydrofuran + Methane) and (2,3-Dihydrofuran + Methane) Clathrate Hydrates

Herein, we examined the crystal structure of 2,5-dihydrofuran and 2,3-dihydrofuran clathrate hydrate systems in the presence of methane as help gas. The crystal structure of these systems demonstrates the structure II (sII) clathrate hydrate with the cubic Fd-3m space group. Throughout the inclusion of methane, we observed a decrease in lattice parameters for both 2,5-dihydrofuran and 2,3-dihydrofuran clathrate hydrates. In the (2,5-dihydrofuran + H₂O) or (2,3-dihydrofuran + H₂O) clathrate hydrates, the 2,5-dihydrofuran or 2,3-dihydrofuran molecule is located at the center of the large cages of sII hydrate. However, in the (2,5-dihydrofuran + CH₄) or (2,3-dihydrofuran + CH₄) binary clathrate hydrates, the 2,5-dihydrofuran or 2,3-dihydrofuran molecule is positioned off-center in the large cages of sII hydrate. Finally, we confirmed the possibility increase of host–guest interaction via possible host–guest hydrogen bonding due to the decrease of the shortest distance between host and guest molecules.