Separation of CO_2–N_2 using zeolite NaKA with high selectivity

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 Na KA 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 Na KA 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.

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.