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

Abstract

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).