Replacement of methane hydrate by carbon dioxide: C-13 NMR study for studying a limit to the degree of substitution

Abstract

The results presented here show that, at least in a laboratory setting, the replacement of CH4 by CO2 is favored from the points of view of equilibrium thermodynamics. Pure and mixed-phase hydrates were prepared in porous silica gel in order to observe the guest distribution in hydrate cages by 13C NMR spectroscopy. The resulting ratio values for CH 4 in small and large cages strongly suggested that at least 64% of methane should be recoverable from a hydrate of composition CH 4·05H2O.