Methane Clathrate Hydrates Formed within Hydrophilic and Hydrophobic Media: Kinetics of Dissociation and Distortion of Host Structure

Abstract

The crystal structure and dissociation processes of methane (CH4) hydrates were investigated to better understand their stability in a natural environment. By using powder X-ray diffraction, we found that the unit-cell parameters of the hydrates formed with fine hydrophilic and hydrophobic beads were respectively larger and smaller by 0.02 Å than the unit-cell parameters of simple CH4 hydrates. In addition, it was found that CH4 hydrates formed with hydrophobic beads dissociated quickly above 200 K, whereas the CH4 hydrates formed with hydrophilic beads are stable up to about 273 K (HachikuboPhys. Chem. Chem. Phys. 2011, 13, 17449−17452). The interfacial forces inside the intergranular pores or void spaces of the beads affect the kinetics of dissociation of CH4 hydrate and are important for both the macroscopic and the crystallographic structures.