(609f) Synthesis and Characterization of Polyvinyl Acetate/Zeolite 4A Mixed Matrix Membranes

Project EARTH (Environmentally Applied Research Towards Hydrofluorocarbons) aims to develop processes that are environmentally sustainable and industrially feasible for separating azeotropic hydrofluorocarbon (HFC) refrigerant mixtures so that low global warming potential (GWP) components can be reused in next-generation refrigerants. Some HFCs and HFC mixtures have high GWPs and recent legislation has called for their eventual phase-out. With millions of kilograms of HFCs and HFC mixtures in use with no efficient method for their disposal, companies have begun incinerating or venting these mixtures into the atmosphere, which is harmful to the environment and wastes otherwise reusable refrigerants. This project’s focus is utilizing mixed matrix membranes (MMMs) for the separation of R-410A—a 50-50 weight percent mixture of pentafluoroethane (HFC-125, CHF₂CF₃) and difluoromethane (HFC-32, CH₂F₂). MMMs are a feasible method for separating HFC refrigerant mixtures due to small capital costs and lower energy consumption compared to other separation techniques. Polyvinyl acetate (PVAc) and PVAc/Zeolite 4A MMMs were prepared using dichloromethane as a solvent and the solution casting method. The weight percent of zeolite 4A was varied from 15-35%. Filler distribution and morphology of the MMMs was analyzed using SEM. The compositional characteristics of the pure polymer and MMM were analyzed by FTIR. DSC was used to characterize glass transition temperatures in order to confirm that the polymeric and zeolite phases combined on a molecular level and that improved chemical stability and selectivity was achieved. Permeability of pure polymer and MMM were measured using a static membrane apparatus and pressure rise method. Comparisons of membrane performance and characterization results of the PVAc polymer and MMM will be presented.