Enhanced Separation Performance of Stabilized Olefin Transport Membranes with High-Molecular-Weight Poly(ethylene oxide)

We found that membranes consisting of poly(ethylene oxide) (PEO), AgBF 4 , and Al(NO 3 ) 3 exhibit relatively high permeance, i.e ., 20 gel permeation unit (GPU) with a mixed-gas selectivity of 10 for propylene/propane separation. To enhance separation, high-molecular-weight PEO was utilized as polymer matrix. As a result, when 9.0×10 5 g/mol PEO was utilized, the PEO/AgBF 4 /Al(NO 3 ) 3 electrolyte membranes showed permeance of 32 GPU with a selectivity of 11, as well as demonstrating long-term stability. It was found that longer polymer chains could enable extensive segmental motions that enhance olefin diffusion, thereby improving gas performance. Furthermore, the more viscous aqueous solution of high-molecular-weight PEO enabled the formation of a thinner layer, thus improving the mix-gas permeance of the membrane, using the same conditions as low-molecular-weight PEOs. The coordination interactions of metal ions and ether moieties in the same electrolyte membrane were investigated by FT-IR and X-ray photoelectron spectroscopy.