Study of CO2 separation with PVC/Pebax composite membrane

Separation of CO2 from CH4 is a part of gas sweetening process for natural gas treatment. In the present study, Poly (amide - 6 - b - ethylene oxide) (Pebax MH 1657) copolymer was used as a selective layer to prepare PVC/Pebax composite membrane for CO2 capturing. Gas permeation and transport characteristics of single and mixed gases for CO2 and CH4 were investigated and analyzed using constant pressure method. Trans-membrane pressure and temperature were varied from 5 to 15 bar and 20-50 °C respectively. The temperature dependency of selectivity for CO2/CH4 was decreased noticeably with an increase in temperature, whereas the permeability of both gases increased dramatically. Furthermore, the enhancement of CO2 permeability with increase in gas pressure was probably due to the plasticization of membrane caused by relatively high solubility of CO2 in the membrane. Mixed gases experiments were conducted with different concentration of CO2 at constant temperature and pressure. Permeation measurement showed a steep decline on the membrane selectivity as the partial pressure of CO2 decreased.