(642e) Separation of HFC-32 and HFC-125 Using Amorphous Copolymers of Perfluoro(butenyl vinyl ether) (PBVE) and Perfluoro(2,2-dimethyl-1,3-dioxole) (PDD)

Hydrofluorocarbons (HFCs) are a class of chemical compounds widely used in refrigeration and cooling systems. HFCs were developed to replace chlorofluorocarbon refrigerants that deplete our ozone layer and were regulated by the Montreal Protocol. Although HFCs have zero ozone depletion potential, many HFCs and HFC mixtures have high global warming potentials (GWP). Recent legislation such as the 2020 AIMS act seeks to regulate and phase-out HFC refrigerants by 80% by 2035. With the current legislative focus on the regulations of HFCs, sustainable methods for separating and recycling refrigerants are needed. HFC mixtures are often azeotropic, thus making their separation difficult and energy intensive. Membrane technology provides the opportunity to separate refrigerant mixtures with lower energy consumption and capital requirement compared to other separation methods. Amorphous perfluoropolymers are promising materials for this separation due to their higher affinity for fluorinated penetrants in comparison to hydrocarbon-based polymers as well as their resistance to plasticization. In order to investigate the use of perfluoropolymers for the separation of HFC mixtures, the permeability, solubility, and diffusivity of difluoromethane (HFC-32, CH₂F₂) and pentafluoroethane (HFC-125, CHF₂CF₃), which are components of the widely used refrigerant R-410A, were measured in amorphous copolymers of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD) at a range of compositions. Solubility was modeled using the dual mode sorption model and diffusion coefficients were calculated by fitting kinetic sorption data to a Fickian model. Results indicate high selectivity of HFC-32/HFC-125 at a copolymer composition containing 80 mol% PDD.