Preparation of Cellulose Acetate Hollow-Fiber Membranes for CO ₂ /CH ₄ Separation

Abstract

Abstract The effect of ethanol (EtOH) concentration and air-gap distance on the gas separation performance of cellulose acetate (CA) membrane was studied. CA asymmetric hollow-fiber membranes were prepared through a dry/wet spinning process using nonsolvent-induced phase separation from dope solutions containing N -methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), and EtOH, which were then coated with polydimethylsiloxane. CA hollow-fiber membranes made from C2 dope composition (62 wt% NMP, 23 wt% CA, 10 wt% THF, and 5 wt% EtOH) and air-gap distance of 15 cm exhibited excellent separation properties for CO 2 and CH 4 : 12.9 GPU CO 2 permeance and 43.8 CO 2 /CH 4 selectivity. Results indicated that the air-gap distance and ratio of THF/EtOH in the dope solution play an important role in the spinning process and production of a well-organized skin for CA asymmetric hollow-fiber membranes, which are known to affect the CO 2 /CH 4 separation performance. To verify the separation performance of the prepared membranes, an extensive membrane separation test was conducted using a binary gas (CO 2 /CH 4 60:40). It was demonstrated that methane with purity higher than 97% was recovered at a 77% recovery efficiency in a single-stage permeation.