Selective separation of HFC-32 from R-410A using poly(dimethylsiloxane) and a copolymer of perfluoro(butenyl vinyl ether) and perfluoro(2,2-dimethyl-1,3-dioxole)

Abstract

Currently, millions of kilograms of HFCs and HFC mixtures are in use with no method for efficiently separating the components. Membranes are an attractive method for separating HFC refrigerant mixtures due to both lower energy consumption and capital requirements compared with alternative separation methods such as distillation. This study investigates the use of poly(dimethylsiloxane) and CyclAFlor™, an amorphous copolymer of 5 mol% perfluoro(butenyl vinyl ether) and 95 mol% perfluoro(2,2-dimethyl-1,3-dioxole), for the separation of R-410A, an azeotropic mixture composed of 50 wt% difluoromethane (HFC-32, CH2F2) and 50 wt% pentafluoroethane (HFC-125, CHF2CF3). Pure gas permeability of HFC-32 and HFC-125 were measured using a static membrane apparatus and the pressure-rise method. Solubility and diffusivity were measured using a gravimetric microbalance. Permeability measurements indicate high selectivity of HFC-32 over HFC-125 with CyclAFlor™, and mixed gas selectivity measurements utilizing a mixed gas apparatus are in excellent agreement with ideal selectivity calculations based on solubility and diffusivity measurements. Stability studies indicate that plasticization of the fluorinated amorphous polymer membrane is minimal in the presence of HFC-32 and HFC-125.