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

Abstract

Li8SiO6 and Li4SiO4 were synthesized by a solid-state reaction. Then, dynamic and isothermal thermogravimetric water vapor sorption experiments were performed using two carrier gases: N2 and CO2. Initially, the Li8SiO6–H2O–(N2 or CO2) systems were analyzed. It was evidenced that Li8SiO6 can trap water physically and chemically, producing Li–OH superficial species. When CO2 was used as the carrier gas, Li8SiO6 continued chemisorbing H2O but CO2 was trapped as well, forming Li2CO3 and Li4SiO4 as secondary phases. On the basis of these results, the Li4SiO4–H2O–CO2 system was also analyzed. The experimental results and different theoretical thermodynamic calculations confirmed that Li8SiO6 can chemisorb 2 moles of CO2 per mole of ceramic at a low temperature range (30–80 °C). Finally, different CO2 chemisorption kinetic experiments were performed to analyze and quantify the trapped CO2.