Lithium aluminates (LiAlO(2) and Li(5)AlO(4)) were synthesized, characterized, and tested as possible CO(2) captors. LiAlO(2) did not seem to have good qualities for the CO(2) absorption. On the contrary, Li(5)AlO(4) showed excellent behavior as a possible CO(2) captor. Li(5)AlO(4) was thermally analyzed under a CO(2) flux dynamically and isothermically at different temperatures. These results clearly showed that Li(5)AlO(4) is able to absorb CO(2) 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 CO(2) absorption at low temperatures. However, at high temperatures, once the lithium diffusion is activated, the sintering effect did not interfere with the CO(2) absorption. Eyring's model was used to determine the activation enthalpies of the CO(2) absorption (15.6 kJ/mol) and lithium diffusion (52.1 kJ/mol); the last one is the limiting process.

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The α- and β-Li5AlO4 polymorphs were synthesized using a solid-state reaction. The polymorphs were then characterized by X-ray diffraction (XRD), X-ray thermodiffraction (XRTD), and N2 adsorption. To determine the CO2 chemisorption capacity, the lithium aluminate polymorphs were analyzed thermogravimetrically in the presence of a CO2 flux. In addition, a cyclability study was performed on these ceramic materials. Although the results appear very similar for the two phases, α-Li5AlO4 exhibits a better CO2 chemisorption performance. The cyclic performance tests indicate that both materials exhibit a gradually reduced chemisorption capacity after multicycle processes. However, even after many cycles, the chemisorption capacity is considerably high in comparison to other lithium ceramics tested as CO2 absorbents.

α-Li 5 AlO 4 was synthesized using a solid-state reaction, and then different water sorption experiments were performed using N 2 and CO 2 as carrier gases. When the N 2 −H 2 O flow gas was used, α-Li 5 AlO 4 showed a water vapor sorption because of two different processes: superficial hydration and hydroxylation. However, if CO 2 was used as the water vapor carrier gas, the α-Li 5 AlO 4 carbonation process was observed at low temperatures (30−80 °C), although this reaction is only produced at high temperatures (200−700 °C) under dry conditions. In this case, the carbonation process was induced by the lithium ceramic superficial hydroxylation. The results clearly showed that α-Li 5 AlO 4 is capable of chemisorbing up to 8.4 mmol of CO 2 /g of ceramic, a considerably high capture at low temperatures compared to different materials. Finally, a kinetic analysis indicated that the CO 2 chemisorption in α-Li 5 AlO 4 is highly favored in the presence of water vapor.

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