Calcium Oxide Based Sorbents for Capture of Carbon Dioxide at High Temperatures

Abstract

Calcium oxide is a promising sorbent for the capture of carbon dioxide. In this work, CaO sorbents were prepared using different precursors, including Ca(NO 3 ) 2 ·4H 2 O, CaO, Ca(OH) 2, CaCO 3, and Ca(CH 3 COO) 2 ·H 2 O. Of these, the sorbent prepared from calcium acetate (CaAc 2 −CaO) resulted in the best uptake characteristics for CO 2 . This sorbent had a higher BET surface area and larger pore volume than the other sorbents. According to SEM images, this sorbent exhibits a “fluffy” structure, which probably contributes to its high surface area and large pore volume. This sorbent also showed almost 100% carbonation, at temperatures between 550 and 800 °C. Moreover, the carbonation progressed dominantly during an initial short period. Under numerous carbonation/decarbonation cycles, the CaAc 2 −CaO sorbent demonstrated the best reversibility, even in the presence of 10 vol % water vapor. During a 27-cycle operation, the sorbent maintained fairly high conversion of 62 mol % at 700 °C. Pore size distribution measurements indicate that the pore volume decreased as the experimental cycles continued. Silica was doped on the CaAc 2 −CaO sorbent in various weight percentages, but the resultant sorbents did not exhibit better performance under cyclic operation than those without Si dopant.