Pebax–PEG–MWCNT hybrid membranes with enhanced CO2 capture properties

• Three-component Pebax–PEG–MWCNT hybrid membranes were prepared.
• Incorporating MWCNT increased CO2 permeability and CO2/N2 selectivity.
• Incorporating high molecular weight PEGs increased CO2/CH4 selectivity.
• Incorporating low molecular weight PEGs increased CO2/N2 selectivity.

Three-component hybrid membranes comprising Pebax, poly (ethylene glycol) (PEG)-based polymers and multi-walled carbon nanotube (MWCNT) were prepared by simple physical mixing of Pebax solution and MWCNT-containing PEG-based polymer solution. Scanning electron microscope (SEM) images showed an improved dispersion of MWCNT within polymer matrix arisen from the hydrophilic modification of PEG-based polymers. The embedded MWCNT disrupted the polymer chain packing and decreased polymer crystallinity, which was confirmed by X-ray diffraction. Influences of PEG-based polymer type on CO2, N2 and CH4 permeations were investigated: incorporating high molecular weight PEG-based polymers favored CO2/CH4 separation, while incorporating low molecular weight PEG-based polymers favored CO2/N2 separation. All the hybrid membranes displayed enhanced CO2 permeability owing to the increased amorphous phase. With the incorporation of MWCNT, CO2/CH4 selectivity was decreased for the enhanced chain mobility, while CO2/N2 selectivity was increased for the increased amorphous PEO content. In particular, for P-PEGDME(40)–CNT(5) membrane, a CO2/N2 mixed gas selectivity of 108 and CO2 permeability up to 743 Barrer at 10 bar and room temperature were acquired, which showed promising prospect for CO2 capture.