Development of regenerable MgO-based sorbent promoted with K{sub 2}CO{sub 3} for CO{sub 2} capture at low temperatures

To improve their CO{sub 2} absorption capacity, alkali-based sorbents prepared by impregnation and wet mixing method of potassium carbonate on supports such as activated carbon and MgO (KAC130, KACP30, KMg130, and KMgP30), were investigated in a fixed bed reactor (CO{sub 2} absorption at 50-100{sup o}C and regeneration at 150-400{sup o}C). Total CO{sub 2} capture capacities of KMg130-500 and KMgP30-500 were 178.6 and 197.6 mg CO{sub 2}/g sorbent, respectively, in the presence of 11 vol% H{sub 2}O even at 50{sup o}C. The large amount of CO{sub 2} capture capacity of KMgP30-500 and KMg130-500 could be explained by the fact that MgO itself, as well as K{sub 2}CO{sub 3}, could absorb CO{sub 2} in the presence of water vapor even at low temperatures. In particular, water vapor plays an important role in the CO{sub 2} absorption of MgO and KMg130-500 even at low temperatures below 60{sup o}C, in marked contrast to MgO and CaO which can absorb CO{sub 2} at high temperatures. The CO{sub 2} capture capacity of the KMg130-300 sorbent, however, was less than that of KMg130-500 due to the formation of Mg(OH)2 which did not absorb CO{sub 2}. MgO based-sorbents promoted with K{sub 2}CO{sub 3} after CO{sub 2} absorption formedmore » new structures such as K{sub 2}Mg(CO{sub 3}){sub 2} and K{sub 2}Mg(CO{sub 3}){sub 2}.4(H{sub 2}O), unlike KAC130 which showed only the KHCO{sub 3} crystal structure. The new Mg-based sorbents promoted with K{sub 2}CO{sub 3} showed excellent characteristics in that it could satisfy a large amount of CO{sub 2} absorption at low temperatures, a high CO{sub 2} absorption rate, and fast and complete regeneration. 21 refs., 10 figs.« less