Steam Regeneration of Polyethylenimine-Impregnated Silica Sorbent for Postcombustion CO2 Capture: A Multicyclic Study

Steam regeneration of polyethylenimine (PEI)-impregnated commercial grade silica was investigated in a packed bed reactor. Adsorption was performed at 75 degrees C under 10% CO2/N-2, and desorption was carried out under steam at 110 degrees C for 20 consecutive cycles. CO, adsorption capacity was found to decrease by 9 mol % over the period of 20 cycles. No evident signs of sorbent degradation due to PEI leaching or changes in surface morphology and amine functionalities were observed upon characterization of the sorbent after the cyclic study. Most of the loss in adsorption capacity was associated with thermal degradation of the sorbent during drying under N-2 after steam stripping at 110 degrees C. The desorption kinetics during steam stripping was found to be much faster than during N2 stripping. Over 80% of the total CO, was released within the first 3 min of steam injection into the reactor. A separate packed bed study was conducted to investigate the influence of moisture content (5.3-14.7 vol %) in flue gas on the CO, adsorption capacity of PEI-impregnated silica. The presence of moisture had a positive impact on CO2 uptake of the sorbent; a 4-9 mol % increase in CO2 uptake was observed in comparison to the adsorption under dry conditions. However, the presence of moisture increased the heat of regeneration of the sorbent significantly. It was calculated that the energy demand increased approximately 2-fold on introduction of 14.7% moisture compared to that of dry flue gas.