NMR/MRI Study of Clathrate Hydrate Mechanisms

Gao, Siyang; House, Waylon V.; Chapman, Walter G.

doi:10.1021/jp052071w

Cited by 72 publications

(41 citation statements)

References 9 publications

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“…4 For both cases, an understanding of the interaction between the guest molecule and the host framework is crucial for their formation and melting processes, which are still poorly understood. 5 In this brief report, we present results that elucidate this crucial guest-molecule/hostframework interaction and complement a recent paper by some of the authors. 6 We show additional results of the energy landscape of H 2 and CH 4 in the various cages of the host material, and we show further results for energy barriers for all possible diffusion paths of H 2 and CH 4 through the water framework.…”

supporting

confidence: 73%

Ab initioenergetics and kinetics study of H2and CH4in the SI clathrate hydrate

Kolb

Román-Pérez

et al. 2011

Phys. Rev. B

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We present ab initio results at the density functional theory level for the energetics and kinetics of H 2 and CH 4 in the SI clathrate hydrate. Our results complement a recent article by some of the authors [G. Román-Pérez et al., Phys. Rev. Lett. 105, 145901 (2010)] in that we show additional results of the energy landscape of H 2 and CH 4 in the various cages of the host material, as well as further results for energy barriers for all possible diffusion paths of H 2 and CH 4 through the water framework. We also report structural data of the low-pressure phase SI and the higher-pressure phases SII and SH. Clathrate hydrates are crystalline, ice-like structures formed out of water molecules.1 The water framework creates cavities in which gas molecules-typically O 2 , H 2 , CO 2 , CH 4 , Ar, Kr, Xe-can be trapped, which stabilize the framework. The existence of clathrates was first documented in 1810 by Sir Humphry Davy, and clathrates became the subject of intensive studies in the 1930s, when oil companies became aware that clathrates can block pipelines.2 Nowadays, clathrate hydrates are of particular interest for two reasons: (i) they are formed naturally at the bottom of the ocean, where they are often filled with CH 4 .3 These deposits mean a tremendous stock pile of energy, while-at the same time-representing a possible global warming catastrophe if released uncontrolled into the environment through melting; (ii) clathrate hydrates can be used to store H 2 in its cavities and can be a viable hydrogen-storage material (albeit with moderate hydrogen-storage density). 4 For both cases, an understanding of the interaction between the guest molecule and the host framework is crucial for their formation and melting processes, which are still poorly understood. 5 In this brief report, we present results that elucidate this crucial guest-molecule/hostframework interaction and complement a recent paper by some of the authors. 6 We show additional results of the energy landscape of H 2 and CH 4 in the various cages of the host material, and we show further results for energy barriers for all possible diffusion paths of H 2 and CH 4 through the water framework. We also report structural data of the phases SI, SII, and SH.At low pressure, the methane-filled clathrate forms the structure SI, consisting of two types of cages. Guest molecules such as H 2 and CH 4 in the cavities of the clathrate hydrates interact with the water framework through van der Waals forces. But even the water framework itself, i.e., the interaction of water molecules through hydrogen bonds, has a van der Waals component. 9 To capture these effects, we perform here density functional theory (DFT) calculations utilizing the truly nonlocal vdW-DF functional, which includes van der Waals interactions seamlessly into DFT. [10][11][12] We implemented vdW-DF using a very efficient FFT formulation 13 into the latest release of PWSCF, which is a part of the QUANTUM-ESPRESSO package.14 For our calculations we used ultrasoft pseudopotentials with a kinet...

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supporting

confidence: 73%

Ab initioenergetics and kinetics study of H2and CH4in the SI clathrate hydrate

Kolb

Román-Pérez

et al. 2011

Phys. Rev. B

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“…Hydrate decomposition is a sequence of lattice destruction and gas desorption processes. The formation and decomposition of gas hydrates is complex and not fully understood (Bishnoi and Natarajan, 1996;Gao et al, 2005). The stability conditions are likely to be altered with the presence of varying ionic content of water and the admixture of different constituent gases ( Fig.…”

Section: Decomposition or Dissociationmentioning

confidence: 99%

Geological Hazards

Rajput¹

2016

Geological Controls for Gas Hydrate Formations and Unconventionals

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“…To our knowledge, this is the first time that the 2 MHz NMR T 2 distribution technique has been successfully applied to study gas hydrates. The influence of a hydrate phase on the coexisting fluid structure [27] was also suggested by the change in T 2 of THF in the liquid phase as the solid to liquid ratio changed at the hydrate equilibrium temperature. Since the area under the proton T 2 distribution of the hydrate phase represents the population of the enclathrated THF molecules, an extension of this technique can provide information on intrinsic hydrate kinetics.…”

Section: Introductionmentioning

confidence: 98%