Analysis of the CO₂–H₂O Chemisorption in Lithium Silicates at Low Temperatures (30–80 °C)

Abstract

Li 8 SiO 6 and Li 4 SiO 4 were synthesized by a solid-state reaction. Then, dynamic and isothermal thermogravimetric water vapor sorption experiments were performed using two carrier gases: N 2 and CO 2 . Initially, the Li 8 SiO 6 −H 2 O−(N 2 or CO 2 ) systems were analyzed. It was evidenced that Li 8 SiO 6 can trap water physically and chemically, producing Li−OH superficial species. When CO 2 was used as the carrier gas, Li 8 SiO 6 continued chemisorbing H 2 O but CO 2 was trapped as well, forming Li 2 CO 3 and Li 4 SiO 4 as secondary phases. On the basis of these results, the Li 4 SiO 4 −H 2 O−CO 2 system was also analyzed. The experimental results and different theoretical thermodynamic calculations confirmed that Li 8 SiO 6 can chemisorb 2 moles of CO 2 per mole of ceramic at a low temperature range (30−80°C). Finally, different CO 2 chemisorption kinetic experiments were performed to analyze and quantify the trapped CO 2 .

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

“…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.…”

“…Nevertheless, the combustion of these materials, along with the diverse activities that produce high amounts of CO 2 , has led to a drastic increase in the atmospheric concentration of CO 2 . From 1960 to 2014, the atmospheric concentration of CO 2 has increased from 310 to 400 ppm, contributing directly to the greenhouse effect and global warming . Moreover, as the use of fossil fuels is expected to remain as the main source of energy in the next decades, anthropogenic CO 2 emissions are likely to increase .…”

“…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 .…”

“…In most of these reports, lithium or sodium ceramics have shown an increment in their CO 2 sorption capacities compared with dry conditions at temperatures lower than 100 °C . The improvement in CO 2 chemisorption capacity under these physicochemical conditions has been associated with the production of superficial hydroxyl species, which increase the affinity between the ceramic surface and CO 2 …”

Use of steel slag for CO2 capture under realistic calcium-looping conditions

“…[35][36][37][38] A proposed modication of the CaL process is to introduce a recarbonation stage at high CO 2 partial pressure and high temperature aer carbonation, which is intended to reactivate the regenerated CaO sorbent even though it would involve increasing the cost and complexity of the process.…”