Adsorption separation of CO₂ from simulated flue gas mixtures by novel CO₂ 'molecular basket' adsorbents

Adsorption separation of CO₂ from simulated flue gas mixtures containing CO₂, O₂, and N₂ by using a novel CO₂ 'molecular basket' adsorbent was investigated in a flow adsorption separation system. The novel CO₂ 'molecular basket' adsorbents were developed by synthesising mesoporous molecular sieve MCM-41 and modifying it with polyethylenimine (PEI). The influence of operation conditions, including feed flow rate, temperature, feed CO₂ concentration, and sweep gas flow rate, on the CO₂ adsorption/desorption separation performance and CO₂ breakthrough were examined. The CO₂ adsorption capacity was 91.0 ml (STP)/g-PEI, which was 27 times higher than that of the MCM-41 alone. Further, the adsorbent showed separation selectivity of greater than 1000 for CO₂/N₂ ratio and approximately 180 for CO₂/O₂, which are significantly higher than those of the MCM-41, zeolites, and activated carbons. Cyclic adsorption/desorption measurements showed that the CO₂ 'molecular basket' adsorbent was stable at 75°C. However, the CO₂ 'molecular basket' adsorbent was not stable when the operation temperature was higher than 100°C.