Toward the Efficient Production of Methane/Propane Double Hydrate

Abstract

Propane hydrate has been studied to investigate its use as a possible storage medium for methane gas. For practical purposes, hydrate formation needs to be efficient at near ambient conditions. Ice particles exposed to varying mixtures of propane and methane gas are found to form the double hydrate efficiently and may be quite effective for storing methane. For instance, exposure of the ice particles to a 2/1 methane/propane gas mixture for 18 h converts 66% of the ice to hydrate with 77% occupancy of the 512 cages and a final dissociation temperature of 287 K. The samples were then decomposed to determine the pressure versus temperature at a rate of 1 K/h. It was found that deviations from equilibrium were minor. The compositions of the hydrates were determined via gas chromatography. For the 180 μm particles employed in this study, 77% of the water was converted to double hydrate over 72 h. Additional experiments were performed in which the ice particles were sequentially exposed to propane and then met...