CO2 absorption and regeneration of alkali metal-based solid sorbents

Potassium-based sorbents were prepared by impregnation with potassium carbonate on supports such as activated carbon (AC), TiO2, Al2O3, MgO, SiO2 and various zeolites. The CO2 capture capacity and regeneration property were measured in the presence of H2O in a fixed-bed reactor, during multiple cycles at various temperature conditions (CO2 capture at 60 degrees C and regeneration at 130-400 degrees C). Sorbents such as K2CO3/AC, K2CO3/TiO2, K2CO3/MgO, and K2CO3/Al2O3, which showed excellent CO2 capture capacity, could be completely regenerated above 130, 130, 350, and 400 degrees C, respectively. The decrease in the CO2 capture capacity of K2CO3/Al2O3 and K2CO3/MgO, after regeneration at temperatures of less than 200 degrees C, could be explained through the formation of KAl(CO3)(2)(OH)(2), K2Mg(CO3)(2), and K2Mg(CO3)(2)center dot 4(H2O), which did not completely converted to the original K2CO3 phase. In the case of K2CO3/AC and K2CO3/TiO2, a KHCO3 crystal structure was formed during CO2 absorption, unlike K2CO3/Al2O3 and K2CO3/MgO. This phase could be easily converted into the original phase during regeneration, even at a low temperature (130 degrees C). Therefore, the formation of the KHCO3 crystal structure after CO2 absorption is an important factor for regeneration, even at the low temperature. The nature of support plays an important role for CO2 absorption and regeneration capacities. In particular, the K2CO3/TiO2 sorbent showed excellent characteristics in CO2 absorption and regeneration in that it satisfies the requirements of a large amount Of C02 absorption (mg CO2/g sorbent) and fast and complete regeneration at a low temperature condition (1 atm, 150 degrees C). degrees 2005 Elsevier B.V. All rights reserved.