Separation of CO2/N2 by Means of a Carbon Membrane

The permeation and separation performance of an ultramicroporous carbon membrane for separation of CO2/N2 mixtures were investigated. The experiments were conducted using the steady‐state measurement method with pure gases (dead‐end mode) and a CO2/N2 gas mixture (20/80 mol.‐%) (cross‐flow mode) in the temperature range from 293 K to 363 K and at feed pressures of up to 1.4 MPa and atmospheric pressure on the permeate side. The membrane exhibited a selectivity of about 25 and permeability of about 500 Barrer for CO2 in the mixture with N2. The single‐gas measurements do not reflect the membrane performance correctly. An adsorption‐selective effect is assumed to be the main separation mechanism. Moreover, membrane‐aging effects causing blocking due to pore constrictions through adsorption were observed. These pore constrictions lower the permeability, but they raise the selectivity. Operation at high temperatures leads to a reduction of aging effects.