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

Abstract

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.