Development of Potassium- and Sodium-Promoted CaO Adsorbents for CO2 Capture at High Temperatures

Development of highly efficient adsorbents for the high temperature CO2 capture process is crucial for large scale implementation of this technology. In this work, development of novel potassium- and sodium-promoted CaO adsorbents (KCa and NaCa) is discussed, and their CO2 capture performance at high temperatures is presented. A series of KCa and NaCa adsorbents with various K/Ca or Na/Ca molar ratios were developed and tested for CO2 capture at high temperatures ranging from 300 to 400 degrees C. The structural, chemical, and morphological characteristics of the double salts were systematically evaluated before and after exposure to CO2. Our results indicated that CO2 capacity is largely influenced by both K or Na concentration and adsorption temperature. Maximum capacities of 3.8 and 3.2 mmol/g were obtained for KCa and NaCa double salts, respectively, at 375 degrees C and 1 bar. Further investigation of the effect of temperature revealed that the window temperature for operation ranges from 300 to 650 degrees C, while beyond 650 degrees C, the double salts start to decompose and lose capacity. Moreover, it was found that both adsorption kinetics and capacity improve with temperature, with CO2 uptake reaching a maximum at 10.7 mmol/g at 650 degrees C over KCa double salt. This study represents alkali metal-promoted CaO adsorbents as potential high-temperature adsorbents with similar performance to their MgO-based analogues.