Separation and recycling of hydrofluorocarbon refrigerant mixtures with fluoropolymer-coated hollow fiber membranes

Abstract

Many hydrofluorocarbon refrigerants used in air-conditioning and refrigeration equipment are being phased out based on international restrictions to reduce global warming. Over 1 billion kilograms of hydrofluorocarbons are in use, and recycling is imperative to preventing the release of these greenhouse gases into the atmosphere. We report on composite hollow fiber membranes that can efficiently separate a mixture of difluoromethane and pentafluoroethane that is used worldwide in air conditioners. Selective hollow fiber membranes have been fabricated with a single submicrometer coating of a copolymer of 70 mol % perfluoro(butenyl vinyl ether) and 30 mol % perfluoro(2,2-dimethyl-1,3-dioxole) that separates the azeotropic mixture into a permeate stream with a difluoromethane purity of >95 mol %. Rather than incinerating these valuable materials, this technology can be used to recycle nonregulated difluoromethane for future products and recover pentafluoroethane for use as a chemical feedstock, creating a circular economy.