Advanced multiple-layer composite CTA/CDA hollow fiber membranes for CO2 separations

CO2 separation has become an important global agenda because of the requirements of industrial products and CO2-induced global warming. Membrane-based technologies have provided an alternative for CO2 separation. To make membrane-based separation more competitive, membranes must have a high permeance and high selectivity. Herein, we have developed a new high-performance multiple-layer hollow fiber membrane of cellulose triacetate (CTA) and cellulose diacetate (CDA) blends for CO2 separation. CTA and CDA blends were chosen because they have similar chemical structures, good separation performance, economical and green nature. Both single-layer and dual-layer hollow fibers were fabricated by various spinning strategies. The optimized dual-layer membrane spun at outer dope flow rate of 1 mL/min exhibits a CO2 permeance of 45 GPU and an ideal CO2/CH4 selectivity of 30.3 at 2 bar. Comparing with the optimized single-layer hollow fiber spun at 5 cm air gap distance and 15 m/min take-up speed, the former has a 100% higher CO2 permeance without compromising the selec-tivity. The as-produced hollow fibers display a plasticization pressure of about 10 bar. In addition, they have impressive mixed gas CO2/CH4 selectivity of >40 at 2 bar. Therefore, the newly developed dual-layer hollow fiber membranes may have great potential for CO2/CH4 separation.