Analysis of the CO2 chemisorption reaction mechanism in lithium oxosilicate (Li8SiO6): a new option for high-temperature CO2 capture

Abstract

Lithium oxosilicate (Li₈SiO₆) was successfully synthesized via a solid-state reaction. The sample's structure and microstructure were characterized using X-ray diffraction, scanning electron microscopy and N₂ adsorption. The CO₂ chemisorption capacity was evaluated dynamically and isothermally. Li₈SiO₆ was found to chemisorb CO₂ over a wide temperature range with a maximum weight increase of 52.1 wt%, which corresponds to 11.8 mmol CO₂ per gram ceramic. Using different thermogravimetric analyses with some structural and microstructural analyses, a CO₂ chemisorption mechanism could be proposed, and the chemical species formed (Li₄SiO₄, Li₂SiO₃ and Li₂CO₃) during the CO₂ capture process in Li₈SiO₆ could be elucidated. The kinetic parameter values (k) obtained for the Li₈SiO₆–CO₂ reaction were higher than the k values previously reported for the Li₄SiO₄–CO₂ reaction system. Additionally, ΔH^‡ was found to be 53.1 kJ mol⁻¹. According to these results, the Li₈SiO₆–CO₂ chemisorption mechanism depends on the reaction temperature. Thus, Li₈SiO₆ may find potential applications as an alternative for CO₂ capture because of its wide temperature range, CO₂ chemisorption capacity and kinetic parameters.