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 phaselithium zirconate can be formed from a lithium carbonate, zirconia and potassium carbonate mixture of a certain composition in the temperature range of 850-1200 degreesC. 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. (C) 2003 Elsevier B.V. All rights reserved.