Simultaneous effects of temperature and vacuum and feed pressures on facilitated transport membrane for CO2/N2 separation

The facilitated transport of CO2 through an amine-containing polymeric membrane on a nanoporous PES substrate was studied at large feed-to-permeate pressure differentials that are relevant to post-combustion carbon capture. With the selective layer reinforced mechanically by incorporation of carbon nanotubes, the carrier saturation of amino groups by excessive CO2 was observed at high feed or permeate vacuum pressure. Nearly complete carrier saturation was observed at 7 atm feed pressure or a permeate vacuum near ambient pressure. At relatively low vacuum pressures, the vacuum degree and operating temperature affected the CO2 transport simultaneously. A vacuum pressure significantly lower than the water saturation pressure at certain temperature resulted in the dehydration of the selective layer, thereby a reduced CO2 permeance. This dehydration was mitigated at a moderate vacuum pressure. At the moderate vacuum pressure, the nanoporous PES substrate controlled the water permeation, leading to a sufficiently hydrated selective layer with high CO2 permeance and CO2/N-2 selectivity. Overall, the membrane performed well with 0.3-0.6 atm vacuum pressures at 67 degrees C and a feed pressure of 4 atm, achieving the best membrane performance with a CO2 permeance of 1451 GPU and a CO2/N-2 selectivity of 165.