Temperature-gradient assisted gas-dissolved liquid-phase synthesis of clathrate hydrates

A novel laboratory method to synthesize clathrate hydrates in sealed glass tubes is described in this manuscript. It was known that the major obstacle in the synthesis of a gas hydrate is from the slow mass transport through the hydrate layer. To circumvent this problem in a sealed glass tube, we developed a temperature-gradient assisted gas-dissolved liquid-phase reaction. This method allows a clathrate hydrate start to form at the bottom of a glass tube and then grow through the diffusion of gas molecules from the gas phase passing through the liquid water phase to the water-gas hydrate interface. This method takes advantage of the fact that gases diffuse much faster in a liquid phase than in a gas-hydrate solid phase. Three examples to synthesize D2O/Xe, D2O/THF/Xe, and D2O/propane gas hydrates are given. The formations of the first two gas hydrates were verified with Xe-129 and Xe-129 T-1 NMR experiments, and that of the last one was verified with C-13 and H-2-H-1 QEDOR NMR experiments.