Phase equilibrium and crystallographic structure of clathrate hydrate formed in argon+2,2-dimethylbutane plus water system

This paper reports the four-phase (L-w-H-V-L-g) equilibrium conditions for the structure H hydrates formed in argon + 2,2-dimethylbutane. The experiments were performed at temperatures between 275.6 and 284.3 K, and at pressures between 2.91 and 9.41 MPa. The crystallographic structure of the hydrate was identified to be structure H by powder X-ray diffraction measurements. At a given temperature, the equilibrium pressure of the structure H hydrate formed with argon + 2,2-dimethylbutane was lower than that of the structure II pure argon hydrate. The difference in the equilibrium pressure is 8.1-20.9 MPa in the temperature range of 275.6-284.3 K. Among the system using methane, argon, krypton and xenon, the system using argon shows the highest reduction ratio of equilibrium pressures. (C) 2013 Elsevier B.V. All rights reserved.