Porous ceramic hollow fiber-supported Pebax/PEGDME composite membrane for CO2 separation from biohythane

To upgrade the mixed gas of fermentative hydrogen and methane for the preparation of biohythane as a gaseous fuel for vehicles, a composite membrane of poly(amide-b-ethylene oxide) (Pebax® MH 1657) and polyethylene glycol dimethylether (PEGDME) coated on a porous ceramic hollow fiber was originally proposed for CO2 separation. The Pebax/PEGDME selective layer with high CO2 selectivity was closely adhered and evenly distributed to the porous ceramic hollow fiber as a highly permeable support. The ideal CO2/H2 selectivity of the composite membrane increased from 12 ± 0.7 to 26 ± 1.7 when the temperature decreased from 50 °C to 10 °C. Competitive sorption between different gas molecules was found in the composite membrane. The fast diffusion of small molecular gas (H2) through the nanopores in the selective layer improved the diffusion of relatively large molecular gases (CO2 and CH4) in the gas mixture. On the contrary, the slow diffusion of large molecular gas (CH4) worsened the diffusion of relatively small molecular gases (CO2 and H2).