Steam Regeneration of Polyethylenimine-Impregnated\nSilica Sorbent for Postcombustion CO₂ Capture: A Multicyclic\nStudy

Abstract

Steam regeneration of polyethylenimine\n(PEI)-impregnated commercial\ngrade silica was investigated in a packed bed reactor. Adsorption\nwas performed at 75 °C under 10% CO₂/N₂, and desorption was carried out under steam at 110 °C for 20\nconsecutive cycles. CO₂ adsorption capacity was found to\ndecrease by 9 mol % over the period of 20 cycles. No evident signs\nof sorbent degradation due to PEI leaching or changes in surface morphology\nand amine functionalities were observed upon characterization of the\nsorbent after the cyclic study. Most of the loss in adsorption capacity\nwas associated with thermal degradation of the sorbent during drying\nunder N₂ after steam stripping at 110 °C. The desorption\nkinetics during steam stripping was found to be much faster than during\nN₂ stripping. Over 80% of the total CO₂ was\nreleased within the first 3 min of steam injection into the reactor.\nA separate packed bed study was conducted to investigate the influence\nof moisture content (5.3–14.7 vol %) in flue gas on the CO₂ adsorption capacity of PEI-impregnated silica. The presence\nof moisture had a positive impact on CO₂ uptake of the\nsorbent; a 4–9 mol % increase in CO₂ uptake was\nobserved in comparison to the adsorption under dry conditions. However,\nthe presence of moisture increased the heat of regeneration of the\nsorbent significantly. It was calculated that the energy demand increased\napproximately 2-fold on introduction of 14.7% moisture compared to\nthat of dry flue gas.