Molecular Selectivity of CO–N₂ Mixed Hydrates: Raman Spectroscopy and GCMC Studies

This paper reports a novel quantitative investigation concerning the CO selectivity properties for mixed CO–N₂ hydrates. The study was developed by combining Raman scattering experiments and grand canonical Monte Carlo simulations. Both approaches advocate in favor of saying that mixed CO–N₂ hydrates are CO selective and quantitatively compare with regard to the measured and calculated molecular selectivities. Intriguingly, this preferential CO encapsulation is enhanced by decreasing the CO molar fraction of the gas mixture. Here, an original explanation for this peculiar behavior is provided in terms of a structural change of the clathrates from SI to SII and in terms of the thermodynamics of mixtures. This last issue was clearly evidenced by using the ideal adsorption solution theory, which gives results that compare favorably with those obtained from Raman scattering and grand canonical Monte Carlo simulations.