Synthesis and CO₂ sorption properties of pure and modified lithium zirconate

Optimum conditions for synthesis of lithium zirconate by the solid state reaction were studied experimentally. The monoclinic phase lithium zirconate can be formed from a lithium carbonate, zirconia and potassium carbonate mixture of a certain composition in the temperature range of 850-1200 °C. The equilibrium and kinetics of CO₂ sorption on pure lithium zirconate, potassium doped lithium zirconate and potassium doped lithium yttrium-zirconate were studied experimentally by TGA and modeled by gas-solid reaction equilibrium and a simple diffusion model based on the double shell CO₂ sorption mechanism. Both experimental results and thermodynamics analysis show a step function for the isotherms of CO₂ sorption on these materials. The rate of the CO₂ sorption on pure lithium zirconate is controlled by the diffusion of CO₂ in the solid lithium carbonate shell. For potassium doped lithium zirconate or lithium yttrium-zirconate the rate limiting step for CO₂ sorption is shifted to diffusion of oxygen ions in the zirconia shell.