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Experimental Study on the Formation Kinetics of Methane Hydrates in the Presence of Tetrabutylammonium Bromide

Authors
  • Shi, Lingli
  • Shen, Xiaodong
  • Ding, Jiaxiang
  • Liang, Deqing
Publication Date
Aug 01, 2017
Source
GuangZhou Institute of Energy Conversion
Keywords
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Abstract

Tetrabutylammonium bromide (TBAB) could form semiclathrate hydrate under milder conditions compared to gas hydrate and, thus, effectively improve the thermodynamic stability of gas hydrate. To evaluate the effect of TBAB on the formation kinetics of methane hydrates, the kinetic properties of TBAB + CH4 semiclathrate hydrate were investigated with an isobaric method at 7.0 MPa with salt mass fraction and subcooling degree varying from 0.05 to 0.60 and from 4 to 10 K, respectively. The result showed that, with a higher salt concentration and subcooling degree, the induction time presented its stochastic property, while the normalized gas consumption and gas consumption rate were relatively constant and higher, respectively. In addition, Raman spectroscopy, powder X-ray diffraction (PXRD) device, and cryo-scanning electron microscopy were employed to identify the molecular behavior and observe the morphology of the hydrate. The spectra of Raman and PXRD revealed that the CH4 molecules were encaged in dodecahedron cages and its addition induced the orthorhombic pattern, which had the larger potential gas capacity, rather than the tetragonal pattern. The microstructure pictures presented that the addition of TBAB could make the surface of the hydrate more ordered and tight, as a contrary to that of inhibitors, which led to a more chaotic and porous surface. These results could provide important information for hydrate-based industrial applications, such as gas separation and storage.

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