High CO₂Chemisorption in α-Li₅AlO₄at Low Temperatures (30–80 °C): Effect of the Water Vapor Addition

Abstract

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.

CO2—H2O Capture and Cyclability on Sodium Cobaltate at Low Temperatures (30–80 °C): Experimental and Theoretical Analysis

“…All these sorption isotherms present exponential growing trends during relative humidity (RH) increments, from 0% to 80%. Weight increments observed during this sorption stage may be attributed to CO 2 and/or H 2 O sorption on NaCoO 2 , as it has been already shown for other alkaline ceramics . In addition, final sorptions varied as a function of temperature between 30 and 60 °C.…”

“…This means that RH has a higher influence in final weight increments than temperature, at least in this temperature range. If these results are compared with other lithium and sodium ceramics on similar physicochemical conditions, it can be established that NaCoO 2 presents similar CO 2 captures and in some cases even better kinetics than Na 2 SiO 3 and Li 4 SiO 4 , although NaCoO 2 has a lower Na molar ratio content.…”

“…According to those studies, sodium cobaltate and metal‐containing phases are not able to chemisorb CO 2 at low temperatures ( T < 150 °C) in dry conditions. As previously mentioned, water vapor improves CO 2 capture on different alkaline ceramics at low temperatures . Therefore, addition of water vapor may enhance CO 2 chemisorption capacity on NaCoO 2 at such a low‐temperature range.…”

“…In these materials, CO 2 capture at the low‐temperature range and in dry conditions is usually poor, achieving improvements only when the particle surface area is highly increased or when their chemical surface is modified . Nevertheless, it has been reported that these ceramics are able to trap more CO 2 at low temperatures in the presence of water vapor . The alkaline ceramics that have been studied under these conditions are Li 2 ZrO 3 , Na 2 ZrO 3 , Li 5 AlO 4 , CaO, Li 4 SiO 4 , Na 2 SiO 3, and more recently Li 8 SiO 6 and Li 2 CuO 2 .…”

“…[56] Nevertheless, it has been reported that these ceramics are able to trap more CO 2 at low temperatures in the presence of water vapor. [2,[16][17][18][19] The alkaline ceramics that have been studied under these conditions are Li 2 ZrO 3 , Na 2 ZrO 3 , Li 5 AlO 4 , CaO, Li 4 SiO 4 , Na 2 SiO 3, and more recently Li 8 SiO 6 and Li 2 CuO 2 . [2,13,[16][17][18][19]57,58] When reacting with CO 2 , in the presence of water vapor, these alkaline ceramics produce lithium carbonate (Li 2 CO 3 ) or sodium carbonate and/or bicarbonate (Na 2 CO 3 or NaHCO 3 ).…”