Enthalpy of dissociation and hydration number of carbon dioxide hydrate from the Clapeyron equation

Anderson, G. K.

doi:10.1016/s0021-9614(03)00093-4

Cited by 193 publications

(105 citation statements)

References 16 publications

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“…The enthalpy of formation of single guest clathrates is then independent of the clathrate structure, the hydration number n hyd , the gas distribution between cavities, the temperature and the pressure (Avlonitis 2005). His model corroborates in every case the experimental data of Handa (1986a,b) and Anderson (2003) as well as the results of Yoon et al (2003), which were derived by application of the ClausiusClapeyron equation (See Eq. (50)).…”

Section: Enthalpy Of Formation and Dissociation Of Clathratessupporting

confidence: 75%

“…There are mainly two types of structure of clathrate whose cages number and size differ and depend on the size of the trapped molecules. The volatile molecules we consider (CO, CH 4 , CO 2 , H 2 S) can be trapped in clathrates, and all create single guest clathrates of structure I individually (Davidson et al 1987, Dartois 2011Handa 1986b;Anderson 2003;Miller 1961). So, we consider in this model that only the structure I is formed inside the comet nucleus during the formation of MG clathrates.…”

Section: Modeling Parameters Of Clathratesmentioning

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 Clathratessupporting

confidence: 75%

Section: Modeling Parameters Of Clathratesmentioning

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

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“…The computed values are consistent but lower than those computed from theoretical P-T data for bulk hydrates obtained from CSMGem (Center for Hydrate Research Colorado School of Mines, Golden, Colorado, USA) [22] (62.61 kJ/mol) and that from methane-seawater equilibrium data (58.84 kJ/mol) obtained from Duan and Sun [18]. The enthalpies of dissociation reported from experimental investigations of bulk methane hydrates [25] and carbon dioxide hydrates [26] are 54.44 ± 1.45 and 63.6 ± 1.8 kJ/mol, respectively. The values obtained from the post-depressurization data in this study exhibit conditions such as seawater and excess pore pressure developed during thermally induced dissociation of methane hydrates from Ottawa sand-pack (pore diameter: 46-58 µm) under a confining pressure of 10.44 MPa.…”

Section: Kinetics Of Dissociation Of Methane Hydrates By Step-wise Desupporting

confidence: 63%

Formation and Dissociation of Methane Hydrates from Seawater in Consolidated Sand: Mimicking Methane Hydrate Dynamics beneath the Seafloor

et al. 2013

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Methane hydrate formation and dissociation kinetics were investigated in seawater-saturated consolidated Ottawa sand-pack under sub-seafloor conditions to study the influence of effective pressure on formation and dissociation kinetics. To simulate a sub-seafloor environment, the pore-pressure was varied relative to confining pressure in successive experiments. Hydrate formation was achieved by methane charging followed by sediment cooling. The formation of hydrates was delayed with increasing degree of consolidation. Hydrate dissociation by step-wise depressurization was instantaneous, emanating preferentially from the interior of the sand-pack. Pressure drops during dissociation and in situ temperature controlled the degree of endothermic cooling within sediments. In a closed system, the post-depressurization dissociation was succeeded by thermally induced dissociation and pressure-temperature conditions followed theoretical methane-seawater equilibrium conditions and exhibited excess pore pressure governed by the pore diameter. These post-depressurization equilibrium values for the methane hydrates in seawater saturated consolidated sand-pack were used to estimate the enthalpy of dissociation of 55.83 ± 1.41 kJ/mol. These values were found to be lower than those OPEN ACCESSEnergies 2013, 6 6226 reported in earlier literature for bulk hydrates from seawater (58.84 kJ/mol) and pure water (62.61 kJ/mol) due to excess pore pressure generated within confined sediment system under investigation. However, these observations could be significant in the case of hydrate dissociation in a subseafloor environment where dissociation due to depressurization could result in an instantaneous methane release followed by slow thermally induced dissociation. The excess pore pressure generated during hydrate dissociation could be higher within fine-grained sediments with faults and barriers present in subseafloor settings which could cause shifting in geological layers.

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“…Four of these five molecules (CO, CH 4 , CO 2 , H 2 S) form individually a SI structure of clathrate (Davidson et al 1987;Dartois 2011;Handa 1986b;Anderson 2003;Miller 1961) and N 2 is the only one molecule forming a SII-structure (Chazallon & Kuhs 2002;Sloan & Koh 2008), leading to small differences in n hyd . All volatile molecules studied in this work are small enough to enter both the small and large cavities (Sloan & Koh 2008;Gabitto & Tsouris 2010).…”

Section: Thermodynamics Parameters Of Condensation and Clathrate Formmentioning

confidence: 99%

From stellar nebula to planetesimals

Marboeuf

Thiabaud

Alibert

et al. 2014

A&A

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Context. Solar and extrasolar comets and extrasolar planets are the subject of numerous studies in order to determine their chemical composition and internal structure. In the case of planetesimals, their compositions are important as they govern in part the composition of future planets. Aims. The present works aims at determining the chemical composition of icy planetesimals, believed to be similar to present day comets, formed in stellar systems of solar chemical composition. The main objective of this work is to provide valuable theoretical data on chemical composition for models of planetesimals and comets, and models of planet formation and evolution. Methods. We have developed a model that calculates the composition of ices formed during the cooling of the stellar nebula. Coupled with a model of refractory element formation, it allows us to determine the chemical composition and mass ratio of ices to rocks in icy planetesimals throughout in the protoplanetary disc. Results. We provide relationships for ice line positions (for different volatile species) in the disc, and chemical compositions and mass ratios of ice relative to rock for icy planetesimals in stellar systems of solar chemical composition. From an initial homogeneous composition of the nebula, a wide variety of chemical compositions of planetesimals were produced as a function of the mass of the disc and distance to the star. Ices incorporated in planetesimals are mainly composed of H 2 O, CO, CO 2 , CH 3 OH, and NH 3 . The ice/rock mass ratio is equal to 1 ± 0.5 in icy planetesimals following assumptions. This last value is in good agreement with observations of solar system comets, but remains lower than usual assumptions made in planet formation models, taking this ratio to be of 2-3.

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Enthalpy of dissociation and hydration number of carbon dioxide hydrate from the Clapeyron equation

Cited by 193 publications

References 16 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

Formation and Dissociation of Methane Hydrates from Seawater in Consolidated Sand: Mimicking Methane Hydrate Dynamics beneath the Seafloor

From stellar nebula to planetesimals

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