Hydrate phase equilibrium in the system of (carbon dioxide + 2,2-dimethylbutane + water) at temperatures below freezing point of water

Shen, Renkai; Tezuka, Kyoichi; Uchida, Tsutomu; Ohmura, Ryo

doi:10.1016/j.jct.2012.04.014

Cited by 22 publications

(12 citation statements)

References 6 publications

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“…The beneficial property of sH hydrate is the milder phase equilibrium conditions (i.e., lower phase equilibrium pressure and higher temperature) of formation of this phase compared to those of the sI and sII hydrate counterparts. − In the sH hydrate, the large molecule guest compound (LMGC) is captured within large icosahedron 5 12 6 8 (I) cage and small molecule guest compounds (SMGCs) are encapsulated in the small pentagonal dodecahedron 5 12 (D) cage and dodecahedron 4 3 5 6 6 3 (D′) oblate cage; see Figure . The sH phase has a layered structure with alternating layers of D cages and I + D′ cages stacked perpendicular to the direction of the c axis of the unit cell.…”

Section: Introductionmentioning

confidence: 99%

Effect of Nonspherical Encapsulated Guests on the Volumetric Behavior of Structure H Clathrate Hydrates

et al. 2018

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Since its first discovery, technologies utilizing the structure H (sH) clathrate hydrates have been proposed. To develop the technology, understanding the mechanism of thermophysical property manifestation would be of fundamental importance. It is reported in the literature that the molecular properties of guest molecules had a significant influence on the crystal structure and the resulting thermophysical properties of the sH hydrate. In the present study, the effect of linear N 2 help-gas molecule on the crystal structure was experimentally and computationally investigated to focus on the shape of the guest molecule in the sH binary clathrate with neohexane. Powder X-ray diffraction (PXRD) measurements were performed in temperatures from 93 to 183 K. The lattice constant values on a and c axes, the cage occupancies of small 5 12 and 4 3 5 6 6 3 cages, and guest distributions in the host cages were determined. Parrinello−Rahman molecular dynamics (MD) simulations were performed on the sH clathrate hydrate phase. The simulated values of the lattice constants indicated the same tendency as the experimental results. The MD simulations provided detailed descriptions of the molecular motions of guest molecules. On the basis of these results, the influence of a small guest molecule on the crystal structure of sH hydrate is discussed.

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Section: Introductionmentioning

confidence: 99%

Effect of Nonspherical Encapsulated Guests on the Volumetric Behavior of Structure H Clathrate Hydrates

et al. 2018

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“…Finally, the curve in the s-H mixed hydrate systems crosses that of the simple CH 4 hydrate system at the structural phase transition point. For example, CH 4 + cis -4-methylcyclohexanol, xenon + 1,1-dimethylcyclohexane (1,1-DMCH), carbon dioxide + 2,2-dimethylbutane, and methylfluoride + methylcyclohexane mixed hydrate systems exhibit such behavior. In other s-H mixed hydrate systems where such structural phase transition has not been reported, in addition, it has been considered that the s-H mixed hydrate is collapsed and changed to simple CH 4 hydrate at pressures higher than tens of MPa.…”

Section: Introductionmentioning

confidence: 99%

Structure-H Methane + 1,1,2,2,3,3,4-Heptafluorocyclopentane Mixed Hydrate at Pressures up to 373 MPa

et al. 2013

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Thermodynamic stability boundary of structure-H hydrates with large guest species and methane (CH4) at extremely high pressures has been almost unclear. In the present study, the four-phase equilibrium relations in the structure-H CH4 + 1,1,2,2,3,3,4-heptafluorocyclopentane (1,1,2,2,3,3,4-HFCP) mixed hydrate system were investigated in a temperature range of (281.05 to 330.12) K and a pressure range up to 373 MPa. The difference between equilibrium pressures in the structure-H CH4 + 1,1,2,2,3,3,4-HFCP mixed hydrate system and the structure-I simple CH4 hydrate system gets larger with increase in temperature. The structure-H CH4 + 1,1,2,2,3,3,4-HFCP mixed hydrate survives even at 330 K and 373 MPa without any structural phase transition. The maximum temperature where the structure-H CH4 + 1,1,2,2,3,3,4-HFCP mixed hydrate is thermodynamically stable is likely to be beyond that of the structure-H simple CH4 hydrate.

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“…19 They performed the measurements with the various gas phase compositions at the temperatures above 273 K. Based on the phase equilibrium data in the CH 4 + CO 2 + 2,2-dimethylbutane + H 2 O system, they estimated that the structure H hydrate formed with 2,2-dimethylbutane and pure CO 2 would be stable exclusively at the temperatures below 267 K. 19 Beltran and Servio also reported the phase equilibrium data for the system of CH 4 + CO 2 + 2,2-dimethylbutane + H 2 O, thereby stating that structure H hydrates became unstable with the increase of CO 2 concentration in the system. 20 The latest study on the structure H hydrate formed with CO 2 + 2,2-dimethylbutane was reported by Shen et al The phase equilibrium data indicated that the structure H hydrate formed with CO 2 is stable at temperatures below 266 K. 21 However, there is no X-ray diffraction data reported to directly identify the hydrate crystal structure.…”

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Synthesis and characterization of a structure H hydrate formed with carbon dioxide and 3,3-dimethyl-2-butanone

et al. 2013

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Hydrate phase equilibrium in the system of (carbon dioxide + 2,2-dimethylbutane + water) at temperatures below freezing point of water

Cited by 22 publications

References 6 publications

Effect of Nonspherical Encapsulated Guests on the Volumetric Behavior of Structure H Clathrate Hydrates

Effect of Nonspherical Encapsulated Guests on the Volumetric Behavior of Structure H Clathrate Hydrates

Structure-H Methane + 1,1,2,2,3,3,4-Heptafluorocyclopentane Mixed Hydrate at Pressures up to 373 MPa

Synthesis and characterization of a structure H hydrate formed with carbon dioxide and 3,3-dimethyl-2-butanone

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