Hydrate dissociation enthalpy and guest size

Sloan, E. Dendy; Fleyfel, F.

doi:10.1016/0378-3812(92)85082-j

Cited by 192 publications

(126 citation statements)

References 24 publications

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“…They concluded that the enthalpy of formation of MG clathrates increases with increasing size of the guest molecules or more precisely with increasing guest-to-cavity size ratios for the guests in the large cages (and hence the cavity occupation of molecules). This is contradictory to the hypothesis proposed by Sloan & Fleyfel (1992) that the heat of dissociation should be, within size constraints, independent of the type and concentration of the mixed guest gas molecules. In addition, Hachikubo et al (2008) showed that the dissociation enthalpy of MG clathrates composed of CH 4 and C 2 H 6 increases with ethane concentration.…”

Section: Enthalpy Of Formation and Dissociation Of Clathratescontrasting

confidence: 88%

“…Each cage contains a single gas molecule trapped thanks to van der Waals interactions but it is possible to trap several different molecules in a structure composed of several cages. There are mainly two types of structure of clathrates whose formation depends on the size of the trapped molecules (Handa 1986a;Sloan & Fleyfel 1992;Sloan 1998;Rydzy et al 2007). The formation/dissociation of clathrate hydrates occurs by the direct gas-ice interaction between gas phase molecules and crystalline water ice or clathrate hydrate, respectively.…”

Section: Description Of the Physical Nucleus Modelmentioning

confidence: 99%

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A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

Marboeuf

Schmitt

Petit

et al. 2012

A&A

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Context. Current theories, models of cometary nuclei and of ice formation in the protoplanetary disk, and laboratory studies suggest that cometary materials could be formed of pure crystalline water ice, amorphous water ice, clathrate hydrate, or a mixture of these structures of water ice. However, current models of cometary nuclei consider only two forms of ice during the thermodynamic evolution of comets: amorphous and crystalline water ices. Aims. In this work, we have developed a model of cometary nucleus that takes into account all water ice structures and phase changes in order to predict the outgassing profile of volatile molecules that could be measured by the Rosetta mission and can be used to constrain the structural type of ice existing in the interior of the Comet 67P/Churyumov-Gerasimenko, the target comet of the Rosetta mission, and, hopefully, its initial composition. Methods. We added the physic of formation/dissociation of clathrate hydrates in addition to others physical processes that are taken into account in models without clathrate hydrates. All thermal changes, as well as the release and trapping of gas with water phase changes are taken into account. Results. This model describes heat transmission, latent heat exchanges, all water ices structures and transitions (amorphous-to-pure crystalline, amorphous-to-clathrate hydrates and pure crystalline-to-clathrate hydrates and vise versa), sublimation/recondensation of volatile molecules in the nucleus, gas diffusion, gas released and trapped by crystallization and clathrate formation/dissociation processes, as well as gas and dust release and mantle formation at the surface. Applying this model to the comet 67P/ChuryumovGerasimenko, results show different outgassing profiles of volatiles molecules from the nucleus depending on the water ice structure, the distribution of volatile molecules between the "trapped" and "condensed" states in the nucleus and the thermal inertia of its porous matrix. Conclusions. Given these results, we pretend that this model is able to constrain the water ice structure and chemical composition in comets from outgassing profiles of volatile molecules, and especially those of the target comet of the Rosetta mission.

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Section: Enthalpy Of Formation and Dissociation Of Clathratescontrasting

confidence: 88%

Section: Description Of the Physical Nucleus Modelmentioning

confidence: 99%

A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

Marboeuf

Schmitt

Petit

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…The resulting experimental enthalpies of dissociation for several simple and mixed hydrates consisting of carbon dioxide, nitrogen, and THF are listed in table 2. As discussed by Sloan and Fleyfel, (6) the enthalpies of dissociation appear to be relatively constant over a wide range of composition for (carbon dioxide + nitrogen). The guest (0.17CO 2 + 0.83N 2 ) was particularly chosen because of our interest in carbon dioxide recovery from power-plant flue gas.…”

Section: Resultsmentioning

confidence: 92%

“…However, this equation is hard to apply to mixed guests of more than two components. Sloan and Fleyfel (6) constructed a number of plots for some common pure hydrate formers and gas mixtures. Even though their results were challenged by Skovborg and Rasmussen, (7) the relation showed good agreement with Handa's experimental results.…”

Section: Introductionmentioning

confidence: 99%

Enthalpies of dissociation of clathrate hydrates of carbon dioxide, nitrogen, (carbon dioxide+ nitrogen), and (carbon dioxide + nitrogen+ tetrahydrofuran)

Kang

Lee

Ryu³

2001

The Journal of Chemical Thermodynamics

179

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“…Sloan and Fleyfel [19] proposed a heuristic to estimate the heat of hydrate dissociation ( H d ) at temperatures above 273.2 K. They state that, to the first approximation, the heat of dissociation above 273.2 K depends upon the type of cavity occupied and is independent of the type and concentration of the guest gas, within the size constraint. The above method indirectly suggests the resultant structure formed by the mixed gas and has been noted that the values obtained by the method are acceptable for engineering calculations.…”

Section: Co 2 /H 2 /H 2 O Systemmentioning

confidence: 99%

Incipient hydrate phase equilibrium for gas mixtures containing hydrogen, carbon dioxide and propane

Kumar

Englezos

2006

Fluid Phase Equilibria

136

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Hydrate dissociation enthalpy and guest size

Cited by 192 publications

References 24 publications

A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

A cometary nucleus model taking into account all phase changes of water ice: amorphous, crystalline, and clathrate

Enthalpies of dissociation of clathrate hydrates of carbon dioxide, nitrogen, (carbon dioxide+ nitrogen), and (carbon dioxide + nitrogen+ tetrahydrofuran)

Incipient hydrate phase equilibrium for gas mixtures containing hydrogen, carbon dioxide and propane

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