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Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P170
Time-resolved views onto gas hydrate formation and decomposition using
neutron diffraction
Andrzej Falenty 1 , Thomas Hansen 2 , Werner F. Kuhs 1
1 Universität Göttingen GZG, Abteilung Kristallographie, Germany – 2 Institut Laue-
Langevin, Grenoble, France
The kinetics of formation/decomposition processes of gas hydrates is a complicated
multi-phase process, details of which are still largely unknown. Clearly, a better understanding
of these processes will help to answer a number of unsolved geoscientific
questions and may enable a wide range of new industrial and scientific applications in
the field of gas hydrates. Time-resolved neutron diffraction on D20 at ILL/ Grenoble
proved to be of crucial importance to unravel the transformation of ice particles
into gas hydrates taking place in a multistage process [1,2,3] The reaction starts with
nucleation-and-growth and later changes to a diffusion controlled formation. Similarly,
the decomposition reaction of gas hydrates back into ice was followed by time-resolved
neutron diffraction. Here, a complication arises at lower temperatures due to the intermediate
formation of defective, stacking-faulty ice (resembling so-called ice Ic) [4].
Thus, treating the diffraction data calls for a proper description of the stacking faults
in the defective ice formed. We shall report on the progress made in describing the
decomposition reaction followed by time-resolved neutron diffraction and helped by
in-house work using physico-chemical methods and scanning electron microscopy.
[1] D.K. Staykova, W. F. Kuhs, A. N. Salamatin, and T. Hansen (2003) Formation
of Porous Gas Hydrates from Ice Powders: Diffraction Experiments and Multistage
Model. J. Phys. Chem. B 107, 10299-10311
[2] G. Genov, W. F. Kuhs, D. K. Staykova, E. Goreshnik, and A. N. Salamatin (2004)
Experimental studies on the formation of porous gas hydrates. Am. Miner. 89, 1228-
1239
[3] W.F. Kuhs, D.K. Staykova, A.N.Salamatin (2006) Formation of methane hydrate
from polydisperse ice powders. J.Phys.Chem. B xxx (in press)
[4] W. F. Kuhs, G. Genov, D. K. Staykova, and T. Hansen (2004) Ice perfection and
onset of anomalous preservation of gas hydrates. Phys. Chem. Chem. Phys. 6,
4917-4920