Solubility, Diffusivity, and Permeability of HFC-32 and HFC-125 in Amorphous Copolymers of Perfluoro(butenyl vinyl ether) and Perfluoro(2,2-dimethyl-1,3-dioxole)

Abstract

R-410A, an azeotropic mixture composed of 50 wt % difluoromethane (HFC-32, CH2F2) and 50 wt % pentafluoroethane (HFC-125, CHF2CF3) used in residential and commercial air-conditioning applications, will be phased down due to the high global warming potential (GWP) of HFC-125. The HFC-32 can be reused in low-GWP blends containing hydrofluoroolefins (HFOs); however, incumbent separation technology, fractional distillation, cannot separate azeotropic mixtures. Membrane technology provides the opportunity to achieve a selective separation of azeotropic HFC refrigerant mixtures with lower energy consumption and capital requirements. This study explores the use of amorphous perfluoropolymers for the separation of R-410A. The permeability, solubility, and diffusivity of HFC-32 and HFC-125 were measured in copolymers of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD). Pure gas permeability of HFC-32 and HFC-125 were measured using a static membrane apparatus and the pressure-rise method. Solubility measurements were obtained using a gravimetric microbalance, and diffusivity was calculated using a Fickian model. The results indicate that a high permeability and selectivity of HFC-32/HFC-125 can be obtained with a 50 wt % PBVE and 50 wt % PDD copolymer and that the separation is diffusion-driven over the entire range of compositions tested.