Guest distributions and dissociation enthalpy of fluorinated gas (CHF3 or C2F6)+N2 hydrates for hydrate-based gas separation

Fluorinated gases (F-gases), such as CHF 3 and C 2 F 6 , which are used in the semiconductor industry and have considerable global warming potential, can be recovered after use through a gas hydrate-based separation method to prevent their release into the atmosphere. In this study, the guest distributions and dissociation enthalpy (ΔH d ) of F-gas (CHF 3 or C 2 F 6 )+N 2 hydrates with different F-gas concentrations (CHF 3 : 20%, 80%, and 100% and C 2 F 6 : 20%, 60%, 80%, and 100%) were experimentally investigated using a powder X-ray diffractometer and a high-pressure micro-differential scanning calorimeter, respectively. At high N 2 concentrations in the feed gas, the occupancy of N 2 in the small (5 12 ) cages of the F-gas+N 2 hydrates increased significantly. As a result, the F-gas+N 2 hydrates exhibited reduced hydration numbers at high N 2 concentration. The ΔH d values (in kJ/mol gas) of the F-gas (CHF 3 or C 2 F 6 )+N 2 hydrates decreased with increased N 2 concentration. The overall experimental results provide useful insights into the design and operation of gas hydrate-based F-gas separation processes.