Thermochemical Capture of Carbon Dioxide on Lithium Aluminates (LiAlO2 and Li5AlO4): A New Option for the CO2 Absorption

Lithium aluminates (LiAlO2 and Li5AlO4) were synthesized, characterized, and tested as possible CO2 captors. LiAlO2 did not seem to have good qualities for the CO2 absorption. On the contrary, Li5AlO4 showed excellent behavior as a possible CO2 captor. Li5AlO4 was thermally analyzed under a CO2 flux dynamically and isothermically at different temperatures. These results clearly showed that Li5AlO4 is able to absorb CO2 in a wide temperature range (200-700 degrees C). Nevertheless, an important sintering effect was observed during the thermal treatment of the samples, which produced an atypical behavior during the CO2 absorption at low temperatures. However, at high temperatures, once the lithium diffusion is activated, the sintering effect did not interfere with the CO2 absorption. Eyring's model was used to determine the activation enthalpies of the CO2 absorption (15.6 kJ/mol) and lithium diffusion (52.1 kJ/mol); the last one is the limiting process.