Investigation on the effects of air gap distance on the formation of cellulose triacetate hollow fiber membrane for CO2 and CH4 gases permeation

CO 2 removal is essential for the sweetening process of sour natural gas in order to meet the desired specifications for natural gas to be utilized and transported. CO 2 separation from natural gas stream can be achieved through the application of membrane technology which will enable natural gas to be suitable for commercial use. Cellulose triacetate (CTA) is a well-known polymer material for CO 2 removal due to its high affinity towards CO 2 . As compared to flat sheet membranes, hollow fiber configuration is preferable due to its large surface to unit volume ratio and self-supporting characteristics, therefore making it a superior choice compared to other configurations. In this work, fabrication of hollow fiber membranes by employing CTA as a polymer for the separation of CO 2 and CH 4 gases is focused. During fabrication, the air gap distance was varied from 1 cm to 7 cm. Following that, the morphology of the resulting fibers was investigated by using a scanning electron microscope (SEM). Next, the CO 2 and CH 4 gas permeation, and CO 2 /CH 4 gas pair selectivity of the resultant HFMs were assessed using a custom-built gas permeation test rig. In addition, post-treatment of HFM with polydimethylsiloxane (PDMS) was also carried out. Then, the gas permeation and gas pair selectivity of the resultant hollow fiber membranes before and after the PDMS coating were compared. The optimum gas permeation performance of CTA HFM was obtained at an air gap distance of 3 cm and a feed pressure of 3 bar as it yielded the highest CO 2 permeance of 78.77 GPU and CO 2 /CH 4 gas pair selectivity of 2.80. Whereas for PDMS coated CTA HFM, fibers spun at air gap distance of 1 cm demonstrated the highest CO 2 permeance of 14.85 GPU and CO 2 /CH 4 selectivity of 2.54 at feed pressure of 9 bar.