Blends of Fluorinated Additives with Highly Selective Thin-Film Composite Membranes to Increase CO2 Permeability for CO2/N2 Gas Separation Applications

A highly permeable poly(ethylene glycol-b-pentafluoropropyl acrylate) diblock copolymer additive is blended with the highly selective PEBAX 1657 block copolymer and spin coated onto cross-linked poly(dimethylsiloxane) gutter layers coated onto porous polyacrylonitrile supports for use in CO2/N-2 gas separation applications. Blended films containing up to 70 wt % of the fluorinated additive are successfully formed and characterized by scanning electron microscopy, revealing an average film thickness of 200 nm. Addition of the fluorinated additive results in significant enhancements to CO, permeance, in the range of 916 to 1538 GPU while maintaining a CO2/N-2 selectivity between 21 and 33 when blended at 60-65 wt %. The impact of temperature and pressure on membrane performance was determined at temperatures of 25-55 degrees C and pressures of 100-500 kPa. Theoretical calculations of the performance without the gutter layer resistance demonstrate that the corresponding active membrane layer could achieve CO2 permeances between 1128 and 2246 GPU and permeabilities between 226 and 449 barrer with CO2/N-2 selectivities between 27 and as high as 39. The reported thin-film composite membranes represent a significant increase in performance compared with similar polymeric membranes.