Selective Encaging of N2O in N2O–N2 Binary Gas Hydrates via Hydrate-Based Gas Separation

The crystal structure and guest inclusion behaviors of nitrous oxide–nitrogen (N2O–N2) binary gas hydrates formed from N2O/N2 gas mixtures are determined through spectroscopic analysis. Powder X-ray diffraction results indicate that the crystal structure of all the N2O–N2 binary gas hydrates is identified as the structure I (sI) hydrate. Raman spectra for the N2O–N2 binary gas hydrate formed from N2O/N2 (80/20, 60/40, 40/60 mol %) gas mixtures reveal that N2O molecules occupy both large and small cages of the sI hydrate. In contrast, there is a single Raman band of N2O molecules for the N2O–N2 binary gas hydrate formed from the N2O/N2 (20/80 mol %) gas mixture, indicating that N2O molecules are trapped in only large cages of the sI hydrate. From temperature-dependent Raman spectra and the Predictive Soave–Redlich–Kwong (PSRK) model calculation, we confirm the self-preservation of N2O–N2 binary gas hydrates in the temperature range of 210–270 K. Both the experimental measurements and the PSRK model calcula...