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.