Enhancing CO2/CH4 Separation Using Ppo-derived Hollow Fiber Carbon Membrane

Hollow fiber carbon membrane for CO2/CH4 separation was successfully synthesized using poly (2,6-dimethyl-1,4-phenylene oxide) (PPO). Pyrolysis parameters, namely pyrolysis temperature, heating rate, and thermal soak time, were optimized based on CO2 permeability and CO2/CH4 ideal selectivity by using Robeson’s 2008 CO2/CH4 upper bound as reference. The optimum CO2 permeability and CO2/CH4 ideal selectivity were 1205.8 Barrer and 194.8, respectively. The surface morphology of PPO and carbon membranes was dense, homogeneous, and symmetrical, with thickness of approximately 15.4 and 14.7 µm, respectively. The crystallinity of the carbon membrane pyrolyzed at the optimum pyrolysis temperature of 600 °C was highly amorphous. The transport mechanism of CO2 through the optimal carbon membrane was dominated by molecular sieving besides surface diffusion. High pyrolysis temperatures reduced the CO2 permeability and increased the CO2/CH4 ideal selectivity. Increasing the heating rate increased the CO2 and CH4 permeabilities and decreased the CO2/CH4 ideal selectivity. Increasing the thermal soaking time increased CO2 permeability without affecting CH4 permeability, thereby increasing the CO2/CH4 ideal selectivity. The CO2 permeability and CO2/CH4 permselectivity from binary test were similar to the CO2 permeability and CO2/CH4 permselectivity from single gas test because of CO2 surface diffusion through the carbon membrane.