New Pebax®/zeolite Y composite membranes for CO2 capture from flue gas

A new Pebax®/zeolite Y composite membrane with three layers on top of the polyethersulfone (PES) substrate was designed and successfully synthesized for CO2 capture from flue gas. The three layers were the zeolite Y inorganic layer, selective Pebax® layer, and polydimethylsiloxane (PDMS) cover layer, respectively, from bottom to top. Zeolite Y with a particle size of about 40 nm was synthesized and deposited onto the PES substrate. On top of the zeolite Y layer, a selective polymer layer was deposited with the blend solution of Pebax® and ethylene oxide (EO)-containing small molecules. A PDMS cover layer was applied on top of the Pebax® layer for defect abatement. The composite membrane showed a better CO2/N2 separation performance compared to the membrane without the zeolite Y layer, which was due to two reasons. First, the hydrophilic zeolite Y layer improved the adhesion between the Pebax® polymer layer and the substrate, which allowed for the preparation of much thinner and defect-free membranes. Second, the zeolite Y layer had a smaller interparticle pore size than the PES substrate and then minimized the penetration of polymer solution into the pores, which reduced the mass transfer resistance of CO2 molecules through the membrane. The effects of different Pebax® blend compositions and various coating conditions on the membrane separation performance were also investigated. This work for the first time reports a thin Pebax® membrane with a high CO2 permeance and a relatively good CO2/N2 selectivity at 57 °C. The resulting Pebax®/zeolite Y composite membrane exhibited a CO2 permeance up to 940 GPU and a CO2/N2 mixed gas selectivity of 30 at 57 °C, indicating promising potential for CO2 capture from flue gas.