Synthesis and CO ₂ Adsorption Characteristics of Lithium Zirconates with High Lithia Content

Pure monoclinic phase Li 6 Zr 2 O 7 and rhombohedral phase Li 8 ZrO 6 that coexisted with a fraction of Li 6 Zr 2 O 7 , are synthesized by a liquid phase coprecipitation method and characterized by X‐ray diffraction, scanning electron microscopy, and thermo‐gravimetric analysis. The high‐temperature CO 2 uptake properties of both samples are systematically investigated. The temperature effect tests indicate that, in the case of low temperature (<973 K), both of the adsorbents exhibit slow CO 2 uptake rates because of the inhibited diffusion of CO 2 in the solid carbonate shell; while at the temperature above the melting point of Li 2 CO 3 (about 983 K), the CO 2 uptake rates are enhanced dramatically for both Li 6 Zr 2 O 7 and Li 8 ZrO 6 , and achieved about 12.3% weight gain and 35.0% weight gain within 15 min at 1073 K, respectively. The thermal stability tests indicate that both samples exhibit gradually reduced capacities during the multicycle processes. The analysis of the crystalline structure reveals that the reduced capacities are resulted from the loss of lithia under high temperatures. Finally, the possible adsorption pathways for both monoclinic phase Li 6 Zr 2 O 7 and rhombohedral phase Li 8 ZrO 6 are suggested as well.