The properties of CO2 adsorption on monoclinic-phase Li6Zr2O7 (m-Li6Zr2O7) in low CO2 concentration stream are studied and compared with tetragonal-phase Li2ZrO3 (t-Li2ZrO3) using thermogravimetric analysis. The results indicate that because of the higher lithium content, about 86.7% capacity can be preserved for m-Li6Zr2O7 (at 1023 K) as the CO2 partial pressure decreases from 1.0 to 0.1 bar, whereas only about 3.5% capacity is preserved for t-Li2ZrO3 (at 848 K). The multicycle test of m-Li6Zr2O7 in 10% CO2 stream exhibits effective performance of CO2 uptake and release, though the capacity reduces gradually. Further, on the basis of the proposed adsorption pathway, a double exponential model is used to simulate the CO2 adsorption processes on m-Li6Zr2O7 with the activation energy of 22.684 and 56.084 kJ/mol for CO2 and Li+ diffusion, respectively, indicating the Li+ diffusion is the limiting step in the adsorption process.

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Li(8)ZrO(6) contains a high lithium content and may bear a great ability of CO(2) absorption, yet the reports about the properties of CO(2) absorption on Li(8)ZrO(6) are few to date for its difficulty in production. In this paper, high-purity Li(8)ZrO(6) is synthesized via a three-step calcination method combined with an effective lithium source and a suitable initial Li/Zr molar ratio. The produced Li(8)ZrO(6) possesses a great CO(2) absorption capacity of about 53.98 wt % at 998 K, which could be well-maintained in a wide range of CO(2) partial pressures of 0.1-1.0 bar although it decreased gradually during the multicycle process of CO(2) absorption-desorption in a 10% CO(2) feed stream because of the high working temperature. These properties imply that Li(8)ZrO(6) may be a new option for high-temperature CO(2) capture applied in industrial processes such as a steam methane reformer.