Effect of doping K element on properties of lithium zirconate as CO₂-absorbent

With nanometer-sized monoclinic ZrO₂, lithium carbonate, and potassium carbonate as starting materials, potassium-doped lithium zirconate Li₂K_2xZrO₃ (0 ≤ x ≤ 0.4) absorbents are prepared by high-temperature solid-state reaction. The influence of doping potassium on the crystal structure of the prepared absorbents is studied by comparison of their XRD patterns. The microscopic morphologies of absorbents with different x were viewed by a sanning electron microscopy. Their CO₂-absorption abilities were measured with a thermogravimetric analyzer. The experimental results show that doping potassium can significantly improve the CO₂-absorption ability of lithium zirconate. It is found that Li₂K_2xZrO₃ absorbent with x = 0.03 possesses the best performance. As much as (25 ± 0.6)% (wt) of CO₂ was absorbed by such an absorbent from an atmosphere consisting of 20% of CO₂ plus 80% of air at 500°C within 160 min. After 18 absorption-desorption cycles this absorbent lost only 1.1% of its CO₂-absorption capacity. Since no remarkable change in particle size is observed, the performance improvement might be attributed to the creation of lattice defects in the lithium zirconate crystals by doping potassium.