Thermodynamic and structural characteristics of the N2 _+ CHF3 and N2 + C2F6 gas hydrates for hydrate-based F-gas separation

Abstract

The emission of CHF3 and C2F6 to the atmosphere should be reduced in order to mitigate the accelerating global warming effect. To examine the feasibility of the gas hydrate-based F-gas capture, the N2 + CHF3 and N2 + C2F6 gas hydrates were investigated with a primary focus on macroscopic thermodynamic conditions, microscopic structural analyses, and gas separation efficiency. The H-LW-V equilibrium lines of both N2 + CHF3 and N2 + C2F6 hydrates were shifted to thermodynamically more stable region as the concentrations of F-gases increased when compared to pure N2 hydrate. The N2 + CHF3 hydrates were revealed to be sI hydrates, whereas the N2 + C2F6 hydrates were found to be sII hydrates through powder X-ray diffraction. Also, the formation process of both N2 + CHF3 and N2 + C2F6 hydrates was monitored using in-situ Raman spectroscopy. Lastly, the efficiency of gas separation was examined through gas chromatography by measuring gas compositions of both vapor and hydrate phases after the completion of hydrate formation.