Inner-selective polyethersulfone-polydimethylsiloxane (PES-PDMS) thin film composite hollow fiber membrane for CO2/N2 separation at high pressures

Carbon dioxide (CO2) is the dominant greenhouse gas (GHG) and thus CO2 capture from flue gas of power plants, the main anthropogenic source of emission, is a key approach to mitigating the climate change. Thin-film composite (TFC) membranes have received extensive research attention recently as a promising post-combustion CO2 capture (CO2/N2) technology owing to its energy-efficiency, design versatility and upscaling potential. However, studies with the most industrially relevant membrane configuration, the hollow fibers, are rather limited for this application. Herein, we developed an inner-selective polyethersulfone-polydimethylsiloxane (PES-PDMS) TFC hollow fiber membrane by inner coating PDMS in the lumen of PES hollow fibers and then pressurizing the hollow fibers for CO2/N2 separation. The optimal PES-PDMS TFC membrane can achieve a CO2 permeance of 2150 GPU and a CO2/N2 selectivity of 20 when the operating pressure was between 20–22 bar, which holds good potential for post-combustion CO2 capture. The high separation performance arises from a combination of the stretched PES and PDMS layers. The micro-deformation of both layers under high pressures at the lumen side could possibly reduce the selective layer thickness. It may also induce polymer chain orientation, increase the fractional free volume, and potentially create free volume with smaller sizes, thus enhancing the CO₂ permeability and CO₂/N₂ selectivity from the PDMS and PES layers.