Experimental studies on the formation of porous gas hydrates
-
Georgi Genov
,
Werner F. Kuhs
Abstract
Gas hydrates grown at gas-ice interfaces were examined by electron microscopy and found to have a sub-micrometer porous structure. In situ observations of the formation of porous CH4- and CO2- hydrates from deuterated ice Ih powders were made at different pressures and temperatures, using time-resolved neutron diffraction data from the high-flux D20 diffractometer (ILL, Grenoble) as well as in-house gas consumption measurements. The CO2 experiments conducted at low temperatures are particularly important for settling the open question of the existence of CO2 hydrates on Mars. We found that at similar excess fugacities, the reaction of CO2 was distinctly faster than that of CH4. A phenomenological model for the kinetics of the gas hydrate formation from powders of spherical ice particles is developed with emphasis on ice-grain fracturing and sample-consolidation effects due to the outward growth of gas hydrate. It describes (1) the initial stage of fast crack-filling and hydrate film spreading over the ice surface and the two subsequent stages which are limited by (2) the clathration reaction at the ice-hydrate interface and/or by (3) the diffusive gas and water transport through the hydrate shells surrounding the shrinking ice cores. In the case of CO2-hydrate, the activation energies of the ice-surface coating in stage 1 are estimated to be 5.5 kJ/mol at low temperatures and 31.5 kJ/mol above 220 K, indicating that water molecule mobility at the ice surface plays a considerable role in the clathration reaction. Comparable activation energies of 42.3 and 54.6 kJ/mol are observed in the high temperature range for the reaction- and diffusion-limited stages 2 and 3, respectively.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Introductory overview: Hydrate knowledge development
- Scanning Electron Microscopy investigations of laboratory-grown gas clathrate hydrates formed from melting ice, and comparison to natural hydrates
- Dynamics of trimethylene oxide in a structure II clathrate hydrate
- The stability of methane hydrates in highly concentrated electrolyte solutions by differential scanning calorimetry and theoretical computation
- The effect of elevated methane pressure on methane hydrate dissociation
- Methane hydrate formation in partially water-saturated Ottawa sand
- Methanol—inhibitor or promoter of the formation of gas hydrates from deuterated ice?
- Investigating the performance of clathrate hydrate inhibitors using in situ Raman spectroscopy and differential scanning calorimetry
- Physical properties and rock physics models of sediment containing natural and laboratory-formed methane gas hydrate
- Experimental studies on the formation of porous gas hydrates
- Investigation of jet breakup and droplet size distribution of liquid CO2and water systems—implications for CO2hydrate formation for ocean carbon sequestration
- Measurement of clathrate hydrate precipitation from CO2solution by a nondestructive method
- Influence of water thermal history and overpressure on CO2-hydrate nucleation and morphology
- Growth-controlling processes of CO2gas hydrates
- Thermodynamic prediction of clathrate hydrate dissociation conditions in mesoporous media
- Modeling dynamic marine gas hydrate systems
- Late-stage, high-temperature processesing in the Allende meteorite: Record from Ca,Fe-rich silicate rims around dark inclusions
- Partitioning of Sr, Ba, Rb, Y, and LREE between alkali feldspar and peraluminous silicic magma
- Nondestructive three-dimensional element-concentration mapping of a Cs-doped partially molten granite by X-ray computed tomography using synchrotron radiation
- A theoretical study of structural factors correlated with 23Na NMR parameters
- Metamorphic formation of Sr-apatite and Sr-bearing monazite in a high-pressure rock from the Bohemian Massif
- Ultra-deep origin of garnet peridotite from the North Qaidam ultrahigh-pressure belt, Northern Tibetan Plateau, NW China
- Letter. Novel high-pressure behavior in chlorite: A synchrotron XRD study of clinochlore to 27 GPa
- Letter. Periodic precipitation pattern formation in hydrothermally treated metamict zircon
- A high pressure X-ray diffraction study of aragonite and the post-aragonite phase transition in CaCO3
