Magnesia-Stabilized Calcium Oxide Absorbents with Improved Durability for High Temperature CO 2 Capture

Calcium oxide based materials are attractive regenerable absorbents for separating CO 2 from hot gas streams because of their high reactivity, high CO 2 capacity, and low material cost. Their high carbonation temperature makes it possible to recover and use high quality heat released during CO 2 capture, which increases overall process efficiency. However, the performance of all reported CaO-based absorbents deteriorates as the number of carbonation−decarbonation cycles increases. This is caused by absorbent sintering during the highly exothermic carbonation process. We have found that sintering can be effectively mitigated by properly mixing with a modest amount of MgO. A class of CaO-based absorbents with improved durability and CO 2 reactivity were prepared by physical mixing of Ca(CH 3 COO) 2 with small MgO particles followed by high temperature calcination. With 26 wt % MgO content, a CaO−MgO mixture prepared by this method gives as high as 53 wt % CO 2 capacity after 50 carbonation−decarbonation cycles at 758 °C. Without MgO addition, the CO 2 capacity of pure CaO obtained from the same source decreases from 66 wt % for the first cycle to 26 wt % for the 50th cycle under the same test conditions.