Separation of CO2–N2 using zeolite NaKA with high selectivity

The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO2. Using the ion exchange method, different zeolites NaKA varying in K+ content were produced. The adsorption isotherms and kinetic uptakes were measured. The experimental results show that the optimal NaKA could adsorb significant quantities of CO2 and little N2. On the zeolite NaKA with 14.7 at.% K+, the adsorption capacity for pure CO2 is over 3.10 mmol g−1 and the CO2–N2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO2–N2 selectivity could also achieved 200 within 3 min according to the uptake data. To demonstrate the separation effectiveness, breakthrough curves of pure components and binary mixtures were investigated experimentally and theoretically in a fixed bed. It is found that the breakthrough points of CO2 and N2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO2/N2 (20:80, v/v). If the pressure has been increased higher than 0.1 MPa, CO2 would break through the bed much slower than N2. Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.

The zeolite NaKA with 14.7 at.% K+ exchange for NaA has displayed high CO2–N2 selectivity, which demonstrates potential for the separation of CO2–N2 mixtures.Figure optionsDownload as PowerPoint slide