(351af) Separation of Hydrofluorocarbon Azeotropic Mixtures Using Polymeric Membranes

Project EARTH (Environmentally Applied Research Towards Hydrofluorocarbons) is focused on identifying sustainable processes for the selective separation of hydrofluorocarbon (HFC) refrigerant mixtures. HFCs and HFC mixtures were developed to replace chlorofluorocarbons (CFCs), which were linked to the depletion of the Earth’s ozone layer. However, the current concern is some HFCs and HFC mixtures have high global warming potentials (GWPs) and recent legislation such as the Kigali agreement are calling for restrictions in certain applications with an eventual phase-out of HFCs. Currently, millions of kilograms of HFCs and HFC mixtures are in use with no efficient method for their disposal. In order to avoid incinerating or venting HFC refrigerants into the atmosphere—processes that are harmful to the environment and would waste millions of kilograms of refrigerants—Project EARTH aims to develop environmentally responsible methods for separating azeotropic refrigerant mixtures so that low-GWP components can be repurposed into next-generation refrigerants. The initial focus of Project EARTH is the separation of R-410a, a binary azeotropic mixture of 50 wt.% R-32 (CH₂F₂) and 50 wt.% R-125 (CHF₂CF₃), commonly used in air conditioning and heating pump systems. R-32 has a much lower GWP (675) compared with R-125 (3,500) and, if separated, could be reused in new refrigerant blends with hydrofluoroolefins (HFOs). This project focuses on the use of polymeric membranes for the separation of R-410a. Membranes are an attractive method for separating HFC refrigerant mixtures due to lower energy consumption and smaller capital requirements compared with alternative separation methods such as distillation. This presentation will cover current results on the solubility, diffusivity, permeability, and selectivity of R-32 and R-125 in a variety of membrane materials.