(419d) Microscopic Diffusion of Ethylene in 6FDA/DAM – ZIF-8 Mixed Matrix Membranes Using NMR Diffusometry

Mixed-matrix membranes (MMMs) are hybrid porous membranes, which consist of molecular sieve particles dispersed throughout a polymer matrix. In recent years, MMMs have been the subject of intense interest as they represent promising membranes for light gas separations including olefin/paraffin separations. In this work, we present the results of microscopic measurement for self-diffusion of ethylene in a mixed-matrix membrane using NMR-based diffusometry. The mixed-matrix membrane was derived from 6FDA/DAM polymer containing ZIF-8 particles. In addition to the MMM, transport in the constituent components, 6FDA/DAM polymer and ZIF-8, were also investigated which allows direct comparison of transport in the MMM and its precursors. In our diffusion NMR studies we combine the advantages of using large magnetic field gradients and high magnetic field. As a result, observations for diffusion inside the mixed-matrix membrane system for a broad range of microscopic displacements were possible. Three different microscopic diffusion regimes were resolved: ethylene diffusion inside the molecular sieve particles, transport in the polymer matrix between the particles and exchange of ethylene molecules between the molecular sieve particles and the polymer matrix. The results of these measurements will be presented and compared for diffusion of ethylene inside the MMM and the precursor polymer as well as molecular sieve particles.