Stabilization of potassium-doped activated carbon by amination for improved CO2 selective capture

• K-based sites were stabilized on activated carbon by a novel post-amination method.
• Achieved high CO2 adsorption amount for 10% and 0.3% levels compares with 100% feed.
• Regeneration at 600 °C achieved about 92% stable plateau from 2nd to 4th cycle.
• Selectivity was respectively enhanced from 0.190 and 0.167 to 0.580 and 22.974 for 10 and 0.3% levels.

In an effort to enhance the selective capture of CO2, heat treatment of 1 M KOH-doped activated carbon (AC) under inert (N2) and reducing (NH3) atmospheres was used. With N2 only, modified adsorbent became unstable to air upon retrieval. Therefore, stabilization by amination was employed, which also enabled further use of increased KOH concentration. Amine-stabilized 4 M KOH-doped coal-based AC (N-4K-G2) achieved the highest selectivity, as adsorption amount of 10 and 0.3% CO2 were significantly improved from 0.65 and 0.03 to 2.45 and 2.03 mmol/g respectively, with negligible reduction in the adsorption of pure CO2. Also, estimated selectivities αs,g were enhanced from 0.190 and 0.167 to 0.580 and 22.974 for the respective levels. For the first time, sintered KOH was stabilized on AC by amination to achieve high CO2 selectivity from environmental levels. Regeneration tests at 600 °C showed that thermal refreshment enabled excellent reusability of the prepared sorbent with an estimated efficiency of 90.25% after a three-cycle test.