Replacement of methane hydrate by carbon dioxide: 13C 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 CH4 in small and large cages strongly suggested that at least 64% of methane should be recoverable from a hydrate of composition CH4·6.05H2O.