Na2CO3-doped CaO-based high-temperature CO2 sorbent and its sorption kinetics

Abstract

CaO-based sorbents have received much research attention for high-temperature CO2 capture because of their high theoretical sorption capacities. However, harsh conditions are needed to regenerate CaO-based sorbents, and their high CO2 sorption capacities diminish significantly in cyclic sorption procedures owing to thermal sintering effects. To solve these problems, dopant components have been applied to CaO-based sorbents. In this study, a new CaO-based sorbent containing Na2CO3 was synthesized using a precipitation method. The prepared sorbent (Na2CO3-CaO) was characterized using various analytic methods, and its CO2 sorption performance was studied using thermogravimetric analysis. Na2CO3-CaO showed high CO2 affinity above 600 °C, and its sorption/regeneration kinetics were faster than those of the conventional CaO sorbent. To investigate the CO2 sorption mechanism onto Na2CO3-CaO, the change in crystalline structure with respect to temperature was analyzed using in-situ X-ray diffraction; the results revealed that the double salt Na2Ca(CO3)2 was generated from the reaction of CO2 with CaO and Na2CO3. Kinetic models were also developed to describe the CO2 sorption behavior of Na2CO3-CaO. The results of this study advance our understanding of the effect of alkali metal carbonates on CaO-based sorbents.