Novel Cellulose Triacetate (CTA)/Cellulose Diacetate (CDA) Blend Membranes Enhanced by Amine Functionalized ZIF-8 for CO(2) Separation

Currently, cellulose acetate (CA) membranes dominate membrane-based CO(2) separation for natural gas purification due to their economical and green nature. However, their lower CO(2) permeability and ease of plasticization are the drawbacks. To overcome these weaknesses, we have developed high-performance mixed matrix membranes (MMMs) consisting of cellulose triacetate (CTA), cellulose diacetate (CDA), and amine functionalized zeolitic imidazolate frameworks (NH(2)-ZIF-8) for CO(2) separation. The NH(2)-ZIF-8 was chosen as a filler because (1) its pore size is between the kinetic diameters of CO(2) and CH(4) and (2) the NH(2) groups attached on the surface of NH(2)-ZIF-8 have good affinity with CO(2) molecules. The incorporation of NH(2)-ZIF-8 in the CTA/CDA blend matrix improved both the gas separation performance and plasticization resistance. The optimized membrane containing 15 wt.% of NH(2)-ZIF-8 had a CO(2) permeability of 11.33 Barrer at 35 °C under the trans-membrane pressure of 5 bar. This is 2-fold higher than the pristine membrane, while showing a superior CO(2)/CH(4) selectivity of 33. In addition, the former had 106% higher CO(2) plasticization resistance of up to about 21 bar and an impressive mixed gas CO(2)/CH(4) selectivity of about 40. Therefore, the newly fabricated MMMs based on the CTA/CDA blend may have great potential for CO(2) separation in the natural gas industry.