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

In recent years, the Li 4 SiO 4 adsorbent has become a promising candidate for high-temperature CO 2 capture. The fabrication of micro-structured Li 4 SiO 4 could enhance the capture performance effectively. However, there exists a conflict between the purity and the morphology of prepared micro-structured Li 4 SiO 4 . This study proposed a novel hydrothermal-calcination method, which could produce Li 4 SiO 4 microspheres with great morphology and relatively high purity. The physicochemical properties, CO 2 capture performance and forming mechanisms of Li 4 SiO 4 microspheres are evaluated and investigated systematically. It is found that the hydrothermal process could fabricate micro-spherical LiOH@Li 2 SiO 3 precursor, which was further converted to Li 4 SiO 4 microspheres during the subsequent calcination process. The LiOH@Li 2 SiO 3 precursor could not only maintain the microstructure but also reduce the Li 4 SiO 4 generation temperature, thus improving the morphology as well as the purity of obtained Li 4 SiO 4 microspheres. As a result, the adsorbents could reach a CO 2 capture capacity of 0.167–0.222 g/g within 30 min's adsorption under 15 vol.% CO 2 , and their cyclic stability are diverse depending on the used calcination temperatures. The hydrothermal-calcination contributes to the future preparation of high-performance Li 4 SiO 4 -based CO 2 adsorbents.