Characterization of natural gas hydrates by nuclear magnetic resonance and dielectric relaxation

Davidson, D. W.; Garg, S. K.; Gough, S. R.; Hawkins, R. E.; Ripmeester, John A.

doi:10.1139/v77-512

Cited by 72 publications

(40 citation statements)

References 8 publications

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“…But as n-butane was verified as structure II former the shape of the molecule must also play a certain role. From dielectric [20] and Raman measurements [21] and recently single crystal X-ray diffraction [16] it was shown that n-butane is incorporated into the hydrate cage as its gauche conformer.…”

Section: Guest Molecule Diametermentioning

confidence: 99%

Systematic kinetic studies on mixed gas hydrates by Raman spectroscopy and powder X-ray diffraction

Luzi

Schicks

Naumann

et al. 2012

The Journal of Chemical Thermodynamics

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This study presents results from systematic time-resolved experiments regarding the guest molecule geometry. The in situ observations of formation and dissociation processes of multicomponent hydrates were performed by means of Raman spectroscopy and a newly designed experimental setup including powder X-ray diffraction (PXRD) whose capabilities will be presented here in more detail. Both experimental setups allow investigating hydrate kinetics as a function of pressure, temperature and feed gas composition. The unique feature of both setups is the continuous gas flow providing a constant composition of the gas phase during the whole experiment. This is crucial for the formation of mixed hydrates formed from feed gas mixtures that contain one or more components in low concentrations. The formation of structure II hydrates including C 3 H 8 , iso-C 4 H 10 , n-C 4 H 10 or neo-C 5 H 12 besides CH 4 was analysed according to a multi-step model. For the initial phase it turned out that hydrates grown from the gas mixture containing 2% n-C 4 H 10 and 98% CH 4 have the highest formation rate at defined p,T conditions in comparison to other hydrates formed from gas mixtures containing about 2 vol% of the above mentioned hydrocarbons besides CH 4 . But the reaction mechanisms for each hydrate system emerged to be different. Fur-2 thermore, time-resolved Raman and PXRD experiments were performed to study the formation of structure H hydrates with a low-concentrated large hydrocarbon guest molecule. In case of a gas mixture containing 1% iso-C 5 H 12 and 99% CH 4 the formation of a simple structure I CH 4 hydrate was observed at first. Later on, structure H CH 4 + iso-C 5 H 12 hydrate was formed resulting in a coexistence of both structures.

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Section: Guest Molecule Diametermentioning

confidence: 99%

Systematic kinetic studies on mixed gas hydrates by Raman spectroscopy and powder X-ray diffraction

Luzi

Schicks

Naumann

et al. 2012

The Journal of Chemical Thermodynamics

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“…The clathrate hydrates behaviour has therefore been investigated, among other techniques, by Raman (e.g. Sum et al 1997) and (far-)infrared (Richardson et al 1985;Klug & Whalley 1973;Bertie & Jacobs 1982;Fleyfel & Devlin 1988) spectroscopies, as well as neutron scattering (Gutt et al 2002;Prager & Press 2006) and RMN techniques (Kleinberg et al 2003;Nakayama et al 2003;Davidson et al 1977). Pure methane hydrate forms cubic structure I, with two small watermolecule pentagonal dodecahedron cages (S = 5 12 ) and six large hexagonal truncated trapezohedron cages (L = 5 12 6 2 ) in the unit cell, with the general formula (2S.6L.46H 2 O).…”

Section: Introductionmentioning

confidence: 99%

Methane clathrate hydrate FTIR spectrum

Dartois¹,

Deboffle²

2008

A&A

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Context. The physical behaviour of methane clathrate hydrate, a crystallographic ice crystal is of major importance for both the earth and the stability of gases in many astrophysical bodies (planets, comets, etc.). Aims. We provide an infrared spectroscopic identification for astrophysical methane clathrate hydrates and investigate the crystal field experienced by the trapped molecule. Methods. A methane clathrate crystal was produced in a moderate-pressure optical cell. Using FTIR spectroscopy, the ν 3 asymmetric CH-stretching mode of the entrapped methane molecule is recorded from 7 K to 80 K, then back to 7 K. Results. It is shown that the trapped methane molecules in the clathrate hydrate is a quasi rotor, displaying gaseous behaviour at low temperatures. A series of ro-vibrational specific lines is observed, shifted in frequency by the water-ice cage interactions with the trapped methane molecules. Because these transitions are unique to methane clathrate hydrate, they represent a crucial identification pattern for astrophysical icy bodies at low temperatures, such as comets and/or interstellar grains.

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“…Since the first reports on the spectra of methane, ethane, propane, and isobutene hydrates by Davidson and Garg and their co-workers, [141,142] NMR has been frequently used to determine the structure identification, chemical composition, cage occupancy, and water mobility in gas hydrates, and more recently the magnitude of spin-spin and spin-lattice interactions of gas hydrates, the character of relaxation processes, and their dependence on temperature and pressure. It has also been used to examine various defects, thermal fluctuations, translation, and rotation of molecules in gas hydrates, and to identify the enclathrated guest molecules and their concentrations.…”

Section: Nuclear Magnetic Resonance (Nmr)mentioning

confidence: 99%

Instrumental analysis of gas hydrates properties

Rojas

Lou

2009

Asia-Pacific J Chem Eng

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Gas hydrates attracted intense research interest when it was first recognised some 70 years ago that they were responsible for the blockage of flow lines, valves and well heads, thereby causing great loss of production and other severe safety hazards to the oil and gas industry. After many decades, these compounds are still the topic of research activities in various multi-disciplinary fields, including chemical and petroleum engineering, earth and geophysics, chemistry and environmental sciences. This is not only due to the great impact that these compounds have on the oil and gas industry, but also to the potential applications they have in many evolving areas, including, but not only, natural gas storage and transportation, carbon dioxide sequestration, and sea-water desalination. It is generally accepted that gas hydrates represent the largest source of hydrocarbons on earth, something which has not been appreciated until only recently.Management, either prevention or application or both, of gas hydrates requires a complete knowledge and understanding of the formation, decomposition and inhibition mechanisms of gas hydrates, which in turn demands advanced experimental methods and instrumental techniques for gas hydrate characterisation. This paper reviews a broad range of techniques that have been used for natural gas hydrate characterisation. It includes the basic physical science principles of each method and the gas hydrate properties that each method is capable of detecting, including some modern instrumental analyses that enable direct determination of gas hydrate phases and possible measurement of molecular interactions within the fluid phases. 

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Characterization of natural gas hydrates by nuclear magnetic resonance and dielectric relaxation

Cited by 72 publications

References 8 publications

Systematic kinetic studies on mixed gas hydrates by Raman spectroscopy and powder X-ray diffraction

Systematic kinetic studies on mixed gas hydrates by Raman spectroscopy and powder X-ray diffraction

Methane clathrate hydrate FTIR spectrum

Instrumental analysis of gas hydrates properties

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