High-Temperature CO2 Capture on Li6Zr2O7: Experimental and Modeling Studies

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.