Clathrate and other solid phases in the tetrahydrofuran–water system: thermal conductivity and heat capacity under pressure

Abstract

RUSSELL G. Ross and PER ANDERSSON. Can. J. Chem. 60,881 (1982). Solid phases in the tetrahydrofuran-water (THF-H20) system were investigated in the temperature range 100-260K and at pressures up to 1.5 GPa. Thermal conductivity, h, and heat capacity per unit volume, pc,, were measured, using the transient hot-wire method. We made measurements on solid phases having nominal compositions THF.17H20, THF,7.1H20, and THF.4.6H20, which we refer to as phases a , P, and y , respectively. Phase a is known to be a structure I1 clathrate hydrate, and h for this phase was found to be similarto other crystalline solids which areglass-like in relation to their thermal properties. Low-energy excitations are known to be relevant to the properties of glass-like solids, and, in the case of phase a , were probably rotational vibrations of the THF guest molecules. Phase was similar, and we inferred that it was probably a structure I clathrate hydrate. Phase y behaved nearly like a normal crystal phase at low temperatures, but h became almost independent of temperature near melting. At 1.1 GPa and 130 K, we found evidence that phase a transformed, on pressurization, to a metastable modification which may be a new high-density form of clathrate hydrate. The astrophysical implications of our results were mentioned briefly. RUSSELL G. ROSS et PER ANDERSSON. Can. J. Chem. 60, 881 (1982). On a ttudie les phases solides dans le systkme tetrahydrofuranne-eau (THF-H20) dans un intewalle de temperature allant de 100 a 260 K et des pressions allant jusqu'a 1,s GPa. On a mesure la conductivite thermique, h, et la capaciti calorifique par unite de volume, pc,, en utilisant la methode du fil chaud transitoire. Nous avons effectue ces mesures sur des phases solides ayant des compositions nominales de THF.17H20, THF.7,1H20 et THF4,6H20 que nous disignons respectivement comme phases a,p et y.On sait que la phase a a une structure I1 d'hydrate de clathrate et on a trouvt que, pour cette phase, h est semblable a celui d'autres solides cristallins qui ressemblent des verres si I'on tient compte de leurs proprietes thermiques. On sait que les excitations de faible energie sont relikes aux proprietes des solides ressemblant a des verres et, dans le cas de la phase a, ce sont probablement des vibrations-rotations des molecules-h8tes de THF. La phase P est semblable et nous en diduisons qu'elle a probablement une structure I d'hydrate de clathrate. La phase y se comporte presque comme une phase cristalline normale a basse temperature, mais h devient presqu'indtpendant de la temperature au voisinage du point de fusion. A 1,l GPa et 130 K, nous avons trouve des indications a l'effet que la phase a se transforme, sous pression, en une forme metastable qui peut &tre une nouvelle forme d'hydrate de clathrate a haute densite. Nous mentionnons brikvement les implications astrophysiques de nos resultats.[Traduit par le journal]

Overview on Hydrate Coring, Handling and Analysis

“…This negative temperature dependence might result from methane gas in unconnected, intergranular porosity persisting after compaction. These results are consistent with published results except that Ross et al (1982) found a positive dependence on temperature on tetrahydrofuran (THF) hydrate. In a later development, Freifeld et al (2002) have tried to estimate thermal conductivity of hydrate/sand system using CT scan and their results were consistent with those of Waite et al (2002).…”

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

“…There are limited data on the conductivity of clathrates at low temperatures. Their thermal conductivity has been measured on gas hydrates of structure I as CH 4 (Krivchikov et al 2005a), Xe (Handa & Cook 1987;Krivchikov et al 2006) and ethylene oxide (Cook & Laubitz 1983), and gas hydrates of structure II as tetrahydrofuran (Ross & Andersson 1982;Tse & White 1988;Andersson & Suga 1996;Krivchikov et al 2005b), dioxolane (Andersson & Ross 1983;Ahmad & Phillips 1987) and cyclobutanone (Andersson & Ross 1983) in a wide range of temperatures. It is very challenging to measure the bulk thermal conductivity of a homogeneous continuous solid (Krivchikov et al 2007).…”

Heat Transfer Related to Gas Hydrate Formation/Dissociation

“…They found the influence is a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces, not only porosity. With respect to temperature effect, many studies found that hydrates exhibit a glass-like temperature dependence of thermal conductivity (Andersson and Ross, 1983;Handa and Cook, 1987;Krivchikov et al, 2005Krivchikov et al, , 2006Ross et al, 1981;Ross and Andersson, 1982;Tse and White, 1988). Among these studies, the works of Krivchikov et al (2005Krivchikov et al ( , 2006 are interesting as they found that both methane and xenon hydrates show crystal-like temperature dependence below 90 K, while exhibiting glass-like behavior above 90 K. The effect of pressure has also been investigated by many groups (Andersson and Ross, 1983;Rosenbaum et al, 2007;Waite et al, 2007).…”