Macroscopic defects upon decomposition of CO<sub>2</sub> clathrate hydrate crystals

Arzbacher, Stefan; Rahmatian, Nima; Ostermann, Alexander; Massani, Bernhard; Loerting, Thomas; Petrasch, Joerg

doi:10.1039/c8cp07871h

Cited by 8 publications

(7 citation statements)

References 66 publications

(135 reference statements)

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“…Both, the gas release and the change in color point towards the complete decomposition of the hydrate to gas and ice. The complete decomposition of hydrates slightly below the melting point of ice has been observed before 20 and also reported by other authors. 12,45,54 First signs of sample melting occur only later at approximately 274 K and above.…”

Section: Decomposition Dynamics Of Co-deposited Hydratesupporting

confidence: 83%

“…Moreover it will be interesting to examine, whether super-preservation is related to the recently observed barriers to decomposition, which were explained similarly with variations in sample composition. 20 Such work will not only result in a better understanding of the synthesis procedure on its own, but it can also improve our understanding of hydrate formation, decomposition and self-preservation.…”

Section: Discussionmentioning

confidence: 99%

“…12 Similarly, a thin ice cover cannot readily explain the dependence of self-preservation on the type of guest gas, 8 as well as the difference in dissociation behavior between temperature ramping and rapid depressurization experiments. 12 Moreover, macroscopic defects like pores and cracks 20 complicate the development of a comprehensive model of hydrate decomposition including the effect of self-preservation. Furthermore, the roles of mass and heat transport as well as hydrate composition have not been clarified yet, and more experiments are needed.…”

Section: Introductionmentioning

confidence: 99%

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Co-deposition of gas hydrates by pressurized thermal evaporation

Arzbacher

Rahmatian

Ostermann

et al. 2020

Phys. Chem. Chem. Phys.

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Gas hydrates are usually synthesized by bringing together a pressurized gas and liquid or solid water. In both cases, the transport of gas or water to the hydrate growth site is hindered once an initial film of hydrate has grown at the water-gas interface. A seemingly forgotten gas-phase technique overcomes this problem by slowly depositing water vapor on a cold surface in the presence of the pressurized guest gas. Despite being used for the synthesis of low-formation-pressure hydrates, it has not yet been tested for hydrates of CO 2 and CH 4 . Moreover, the potential of the technique for the study of hydrate decomposition has not been recognized yet. We employ two advanced implementations of the condensation technique to form hydrates of CO 2 and CH 4 and demonstrate the applicability of the process for the study of hydrate decomposition and the phenomenon of self-preservation. Our results show that CO 2 and CH 4 hydrate samples deposited on graphite at 261-265 K are almost pure hydrates with an ice fraction of less than 8%. Rapid depressurization experiments with thin deposits (approx. 330 mm thickness) of CO 2 hydrate on an aluminum surface at 265 K yield identical dissociation curves when the deposition is done at identical pressure. However, hydrates deposited at 1 MPa almost completely withstand decomposition after rapid depressurization to 0.1 MPa, while samples deposited at 2 MPa decompose 7 times faster. Therefore, this synthesis technique is not only applicable for the study of hydrate decomposition but can also be used for the controlled deposition of a super-preserved hydrate.

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Section: Decomposition Dynamics Of Co-deposited Hydratesupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Co-deposition of gas hydrates by pressurized thermal evaporation

Arzbacher

Rahmatian

Ostermann

et al. 2020

Phys. Chem. Chem. Phys.

Self Cite

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“…To date, various observations of dynamic changes in clathrate hydrates have been made indirectly using absorption contrast X-ray CT with contrast agents, − Xe, Kr, or Ar as guests, − and defects or pores in the target samples . The advantage of absorption contrast X-ray CT using monochromatic X-rays over CT using white X-rays is that beam hardening does not need to be corrected.…”

Section: Resultsmentioning

confidence: 99%

X-ray Imaging of Clathrate Hydrates as Gas Storage Materials: Absorption Contrast of Low-Density and Low-Absorption Materials Using Energy-Dependent X-ray Computed Tomography

2022

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Non-destructive observations are useful for analyzing objects embedded in structures, but characterizations of low-density materials co-existing with liquid water or ice are difficult, owing to insufficient contrast produced by X-ray computed tomography (CT). This study demonstrates the contrast between the absorption contrast X-ray images of clathrate hydrates and water as a function of the X-ray energy using monochromatic X-rays. Quantitative characterization of the contrast change in the absorption contrast X-ray CT of resins and clathrate hydrates indicates that X-ray CT measurements using monochromatic X-rays are advantageous for the segmentation of carbon dioxide hydrates co-existing with ice but not for methane or tetrahydrofuran hydrates. This can help in the application of absorption contrast X-ray imaging to previously challenging three-dimensional (3D) studies on gas storage processes in materials, such as shale or active carbon, based on their macroscopic 3D structures.

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“…Based on Clarke's study, 18 it is assumed that the dissociation rate can be considered as a pseudo first-order reaction with respect to the fugacity difference. Thus, the dissociation rate constant (k d ) reflects the dissociation rate directly, and can be calculated by Eqns (9)(10)(11).…”

Section: Data Reductionmentioning

confidence: 99%

Experimental study on in situ dissociation kinetics of CO₂ hydrate in pure water and water/sediments systems

Wang

Liu

et al. 2021

Greenhouse Gases

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Recently, hydrate technology as a newly emerging field has been attracting more and more attention. To support its potential applications, the dissociation behaviors and kinetics of CO 2 hydrate in pure water and water/sediments systems at specified temperatures were studied experimentally by depressurization method. This work reveals two novel aspects of CO 2 hydrate dissociation. Firstly, it is remarkable that the dissociation rate of CO 2 hydrate in water/sediments is faster than that of CO 2 hydrate in pure water, which has not been conscious previously. Secondly, a pseudo first-order kinetic equation including the kinetic constant and activation energy was formulated to describe the dissociation process. Temperature plays an important role and the dissociation rate constant (k d ) and activation energy ( E a ) were obtained through the dissociation experiments at different temperatures. For CO 2 hydrate in pure water, the dissociation rate constant increased from 0.02 to 0.13 mol/(dm 2 MPamin) at the temperature from 273.86 to 276.11 K, and the activation energy was 469.06 kJ mol −1 . For CO 2 hydrate in water/sediments, the dissociation rate constant was from 0.03 to 0.15 mol/(dm 2 MPamin) at the temperature ranging from 273.45 to 276.11 K, and the activation energy was 346.30 kJ mol −1 .

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Macroscopic defects upon decomposition of CO₂ clathrate hydrate crystals

Abstract: Cracks and decomposition barriers observed in time-lapse micro-computed tomography measurements challenge existing models of gas hydrate decomposition.

Cited by 8 publications

References 66 publications

Co-deposition of gas hydrates by pressurized thermal evaporation

Co-deposition of gas hydrates by pressurized thermal evaporation

X-ray Imaging of Clathrate Hydrates as Gas Storage Materials: Absorption Contrast of Low-Density and Low-Absorption Materials Using Energy-Dependent X-ray Computed Tomography

Experimental study on in situ dissociation kinetics of CO₂ hydrate in pure water and water/sediments systems

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Macroscopic defects upon decomposition of CO2 clathrate hydrate crystals

Abstract: Cracks and decomposition barriers observed in time-lapse micro-computed tomography measurements challenge existing models of gas hydrate decomposition.

Cited by 8 publications

References 66 publications

Co-deposition of gas hydrates by pressurized thermal evaporation

Co-deposition of gas hydrates by pressurized thermal evaporation

X-ray Imaging of Clathrate Hydrates as Gas Storage Materials: Absorption Contrast of Low-Density and Low-Absorption Materials Using Energy-Dependent X-ray Computed Tomography

Experimental study on in situ dissociation kinetics of CO2 hydrate in pure water and water/sediments systems

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Macroscopic defects upon decomposition of CO₂ clathrate hydrate crystals

Experimental study on in situ dissociation kinetics of CO₂ hydrate in pure water and water/sediments systems