A kinetic study of methane hydrate formation

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Gas hydrates are crystalline compounds of gas and water molecules which are thermodynamically stable at elevated pressures and low temperatures. Their formation is the result of the hydrogen bonding properties of water molecules combined with the van der Waals forces of interaction between "guest" solute and "host" water molecules. Interests in gas hydrates, in the past, were focused mainly on establishing the thermodynamic conditions for their formation with very little attention being given to the kinetics of their formation. In the present investigation, the kinetics of methane hydrate formation are studied using a semibatch stirred tank reactor. The temperatures studied in the experiments are 274.2, 276.5, 278.7, 281.0, and 284.0 Kover a pressure ranging from 3 MPa to 10 MPa. The results reveal that the formation kinetics are a function of the surface area of the gas-water interface, temperature, pressure and degree of supercooling. A plausible mechanism describing the formation of gas hydrates is proposed. The controlling mechanism is suggested to involve the interaction of molecules of water monomers with the parent water cluster and the hydrate forming gas molecules. On the basis of the proposed mechanism, a semi-empirical reaction rate model is formulated and correlated with respect to the obtained experimental data. The resultant expression shows a good fit with the data over the entire range studied. The form of the rate expression is anticipated to apply for other gas hydrates as well.
Bibliography: p. 78-80.
Vysniauskas, A. (1980). A kinetic study of methane hydrate formation (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/22214