Developing new alkaline ceramics as possible CO2 chemisorbents at high temperatures: The lithium and sodium yttriates (LiYO2 and NaYO2) cases

Lithium and sodium yttriates (LiYO2 and NaYO2) were synthesized, characterized and tested as possible carbon dioxide (CO2) captors. All the experimental syntheses and analyses were supported by the theoretical thermodynamic calculations, showing that both ceramics would be able to chemisorb CO2 in a wide temperature range. Therefore, both ceramics were prepared by solid-state reaction and structurally characterized. In fact, the structural characterization evidenced that sodium atoms are located in a octahedral close-packed structure, while lithium ions are not so packed. The lithium ions are, indeed, in a highly distorted tetrahedron, tending to square-planar coordination. Then, based on the theoretical and structural analysis, LiYO2 and NaYO2 samples were investigated for the CO2 capture process through dynamic and isothermal thermogravimetric experiments. All these experiments showed that LiYO2 has better CO2 capture properties than NaYO2, which was further correlated with the crystal structures of each ceramic. Furthermore, both ceramics presented similar CO2 capture efficiencies regardless of the CO2 concentration. Finally, LiYO2 sample was tested for cyclic CO2 chemisorption-desorption processes. The obtained results showed that the CO2 capture efficiency is maintained high at least through 10 cycles. Therefore, these alkaline yttriates seem to present interesting alternatives as high and moderate temperature CO2 captors, applicable for post-combustion industrial capture processes.