Phase diagram and high-pressure boundary of hydrate formation in the carbon dioxide-water system.
Experimental investigation of the phase diagram of the system carbon dioxide-water at pressures up to 2.7 GPa has been carried out in order to explain earlier controversial results on the decomposition curves of the hydrates formed in this system. According to X-ray diffraction data, solid and/or liquid phases of water and CO2 coexist in the system at room temperature within the pressure range from 0.8 to 2.6 GPa; no clathrate hydrates are observed. The results of neutron diffraction experiments involving the samples with different CO2/H2O molar ratios, and the data on the phase diagram of the system carbon dioxide-water show that CO2 hydrate of cubic structure I is the only clathrate phase present in this system under studied P-T conditions. We suppose that in the cubic structure I hydrate of CO2 multiple occupation of the large hydrate cavities with CO2 molecules takes place. At pressure of about 0.8 GPa this hydrate decomposes into components indicating the presence of the upper pressure boundary of the existence of clathrate hydrates in the system.
Nikolaev Institute of Inorganic Chemistry SB RAS, Akademii, Lavrentiev Avenue, 3, Novosibirsk, 630090, Russian Federation. manakov@che.nsk.su
Andrej Yu
AY
Manakov
Yuriy A
YA
Dyadin
Andrey G
AG
Ogienko
Alexander V
AV
Kurnosov
Eugeny Ya
EY
Aladko
Eduard G
EG
Larionov
Fridrih V
FV
Zhurko
Vladimir I
VI
Voronin
Ivan F
IF
Berger
Sergei V
SV
Goryainov
Anna Yu
AY
Lihacheva
Aleksei I
AI
Ancharov