Separation of CO 2 –N 2 using zeolite NaKA with high selectivity

Abstract

Abstract The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO 2 . 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 CO 2 and little N 2 . On the zeolite NaKA with 14.7 at.% K + , the adsorption capacity for pure CO 2 is over 3.10 mmol g −1 and the CO 2 –N 2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO 2 –N 2 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 CO 2 and N 2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO 2 /N 2 (20:80, v/v). If the pressure has been increased higher than 0.1 MPa, CO 2 would break through the bed much slower than N 2 . Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.