Absorption Separation of Hydrofluorocarbon/Hydrofluoroolefin Refrigerant Mixtures Using Ionic Liquids

Separation of hydrofluoroolefins (HFOs)/hydrofluorocar-bons (HFCs) from new-generation refrigerant mixtures has become critical to promote refrigerant recycling use and greatly reduce the emission of HFC refrigerants having high global warming potential. In this study, the utilization of ionic liquids (ILs) as ideal separation agents is explored for the separation performance of mixtures of HFCs (R-32, R-227ea, R-134a, R-152a, and R-125) with HFOs (R-1234yf and R-1234ze(E)). The thermodynamic absorption equilibria of R-134a, R-227ea, R-152a, R-32, and R-125 in [P-6,P-6,P-6,P-14][Cl] were measured at temperatures from 293.15 to 343.15 K and pressure up to 1.4 MPa. R-227ea shows the highest solubility, while R-32 shows the lowest solubility, suggesting that the absorption of HFCs in ILs is mainly related to their H-bonding capability. The measured data were successfully correlated by the equilibrium equation combined with the NRTL model, which provides a theoretical tool used for the separation process design. Moreover, the separation capacity was assessed for HFC/HFO blends in imidazolium-and phosphonium-based ILs using ideal selectivity. Considering the ideal selectivity, viscosity, and cost of ILs, [P-6,P-6,P-6,P-14][Cl] may be a good candidate for an entrainer for separating some azeotropic or close-boiling-point HFC/HFO mixtures.

Automated summary

This study explores the use of ionic liquids as separation agents for the separation of HFC/HFO mixtures. The results show that ionic liquids can effectively absorb HFCs, with R-227ea showing the highest solubility. The absorption equilibria were successfully correlated using the measured data and the NRTL model, providing a theoretical tool for the design of separation processes.