Permeability and selectivity study of natural gas with CO2, N2, and O2 using polyacrylonitrile (PAN) membrane

The permeability and the selectivity of CH4, CO2, N2, and O2 were determined in a polymer membrane prepared from 8% weight ratio PAN powder and 92% weight ratio of dimethylformamide (DMF) as a solvent, commercially known as Polyacrylonitrile (PAN) membrane. Flat sheet membrane with an average thickness of 0.025cm was produced manually using casting knife. Permeability test was conducted with a permeability/permeation unit where the volumetric flow rates of the effluent were measured by a bubble soap flow meter. This polymer exhibits higher permeability of CH4 compare with CO2, N2, and O2. Higher selectivity also achieved for CH4 compare with CO2, N2, and O2 under low pressure and high volumetric flow rates. On the basis of a best fit of the natural logarithm of permeability versus inlet flow rate, PAN membrane should have much higher permeability of CH4 when it is applied with higher inlet flow rate under low feed pressure. For this experiment, the prepared membrane gave the best permeability and selectivity reading at 0.5bar and 0.3 liter per minute of flow rate. Pure gas CO2/CH4 separation properties of this polymer are comparable with those of some other polymers considered for natural gas purification. When exposed to a feed stream with higher pressure, the permeability of CO2, N2, and O2 were high indicates the separation process was not that successful. Successful separation process was achieved at low feed stream pressure and high inlet flow rates.-Author-