Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011),
Edinburgh, Scotland, United Kingdom, July 17-21, 2011.
NEW MEASUREMENTS OF THE EQUILIBRIUM DATA OF METHANE,
CARBON DIOXIDE AND XENON CLATHRATE HYDRATES BELOW
THE FREEZING POINT OF WATER
Nicolas FRAY, Ulysse Marboeuf, Olivier Brissaud and Bernard Schmitt
Laboratoire de Planétologie de Grenoble,
Université Joseph Fourier, CNRS / INSU
BP 53, 38041 Grenoble Cedex 9, FRANCE
LISA, CNRS,
Université Paris Est Créteil, Université Paris Diderot
61 Avenue du Général de Gaulle
94000 Creteil, France
ABSTRACT
We present new HIV measurements of the equilibrium pressure of single guest component clathrate
hydrates of xenon, carbon dioxide and methane at low temperature (< 246K) and low pressure (< 1 bar).
The measured data are compared with the other data reported in the literature and are used to determine
semi-empirical laws allowing us to calculate the equilibrium pressure of these pure clathrates at any
temperature relevant to the astrophysical environments below the freezing point of water. These relations
can be used in astrophysical models such as those devoted to the studies of the cooling and condensation of
the solar nebula or to the ones of the physico-chemical evolution of cometary nuclei and their gas
production along their elliptic orbit.
Keywords: clathrate hydrate, I-H-V equilibrium, CH4, CO2, Xe, Titan, comet, mars, solar nebula
INTRODUCTION
Although no clathrate hydrate has been detected so
far in astrophysical environments, it has been
proposed since a long time that clathrate hydrates
could play a significant role in the chemistry of the
solar nebula and in the physical evolution of
numerous astrophysical objects[1-2-3-4-5].
As it is of interest for the natural gas industry and
for the studies of clathrate hydrates present in the
seafloor, the LW-H-V three-phase equilibrium
(Liquid Water (LW) + clathrate Hydrate (H) +
guest vapor (V)) of simple or mixed clathrate
hydrates at temperature higher than the freezing
temperature of water has been extensively studied.
Nevertheless, in the astrophysical environments,
the temperature is very low compared to the
freezing temperature of water. Thus, LW-H-V
equilibrium data are not relevant for most
astrophysical applications. The I-H-V three-phase
equilibrium (water Ice (I) + clathrate Hydrates (H)
+ guest Vapor (V)) for clathrate hydrates at
temperature below the freezing temperature of
water is important for most astrophysical studies
such those of the cooling and condensation of the
solar nebula, cometary nuclei, Titan hydrocarbon
reservoirs or Mars polar caps. Despite the
importance of the phase equilibrium data at
temperatures below the freezing temperature of
water, there is a paucity of data in contrast to the
ones at temperatures above the freezing
temperature of water.
Miller [5] argued that clathrate hydrates could be
present on most of the objects of the outer solar
system as they incorporate molecular species at
vapor pressures lower than those of the pure ices
of those species. Lewis [6] and Sill and Wilkening
[7] seem to be the first to investigate the possible
formation of clathrate hydrates during the cooling