Hydrothermal-calcination synthesis of lithium orthosilicate microspheres for high-temperature CO2 capture

In recent years, the Li4SiO4 adsorbent has become a promising candidate for high-temperature CO2 capture. The fabrication of micro-structured Li4SiO4 could enhance the capture performance effectively. However, there exists a conflict between the purity and the morphology of prepared micro-structured Li4SiO4. This study proposed a novel hydrothermal-calcination method, which could produce Li4SiO4 microspheres with great morphology and relatively high purity. The physicochemical properties, CO2 capture performance and forming mechanisms of Li4SiO4 microspheres are evaluated and investigated systematically. It is found that the hydrothermal process could fabricate micro-spherical LiOH@Li2SiO3 precursor, which was further converted to Li4SiO4 microspheres during the subsequent calcination process. The LiOH@Li2SiO3 precursor could not only maintain the microstructure but also reduce the Li4SiO4 generation temperature, thus improving the morphology as well as the purity of obtained Li4SiO4 microspheres. As a result, the adsorbents could reach a CO2 capture capacity of 0.167-0.222 g/g within 30 min's adsorption under 15 vol.% CO2, and their cyclic stability are diverse depending on the used calcination temperatures. The hydrothermal-calcination contributes to the future preparation of high-performance Li4SiO4-based CO2 adsorbents.