Kinetics of Methane Hydrate Decomposition Studied via in Situ Low Temperature X-ray Powder Diffraction

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• 作者：S. Michelle Everett ; Claudia J. Rawn ; David J. Keffer ; Derek L. Mull ; E. Andrew Payzant ; Tommy J. Phelps
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：May 2, 2013
• 年：2013
• 卷：117
• 期：17
• 页码：3593-3598
• 全文大小：322K
• 年卷期：v.117,no.17(May 2, 2013)
• ISSN：1520-5215

文摘

Gas hydrate is known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Based on results from the decomposition of three nominally similar methane hydrate samples, the kinetics of two regions, 180鈥?00 and 230鈥?60 K, within the overall decomposition range 140鈥?60 K, were studied by in situ low temperature X-ray powder diffraction. The kinetic rate constants, k_a, and the reaction mechanisms, n, for ice formation from methane hydrate were determined by the Avrami model within each region, and activation energies, E_a, were determined by the Arrhenius plot. E_a determined from the data for 180鈥?00 K was 42 kJ/mol and for 230鈥?60 K was 22 kJ/mol. The higher E_a in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.