On the thermodynamic stability and structural transition of clathrate hydrates

Gas mixtures of methane and ethane form structure II clathrate hydrates despite the fact that each of pure methane and pure ethane gases forms the structure I hydrate. Optimization of the interaction potential parameters for methane and ethane is attempted so as to reproduce the dissociation pressures of each simple hydrate containing either methane or ethane alone. An account for the structural transitions between type I and type II hydrates upon changing the mole fraction of the gas mixture is given on the basis of the van der Waals and Platteeuw theory with these optimized potentials. Cage occupancies of the two kinds of hydrates are also calculated as functions of the mole fraction at the dissociation pressure and at a fixed pressure well above the dissociation pressure.

Digital Object Identifer:10.1063/1.1850904
Published with permission from the copyright holder. This is the institute's copy, as published in Journal of Chemical Physics, Feb 2005, Volume 122, Issue 7.
Publisher URL:http://dx.doi.org/10.1063/1.1850904
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Copyright © 2005 American Institute of Physics