Enhanced high temperature cyclic CO2 capture on Li4SiO4 sorbent from two-dimensional SiO2 nanomeshes

Abstract

The Li4SiO4-based sorbent, noted for its high sorption capacity and lower regeneration temperature, is promising for high-temperature CO2 capture. However, its slower sorption rate and poor cycle stability limit practical applications. In this study, Li4SiO4 was synthesized with various Li/Si molar ratios to serve as CO2 sorbents. The synthesis employed the mechanochemical activation method, effectively addressing challenges like growth, agglomeration, and structural degradation that typically occur during the CO2 sorption process. The results indicate that a smaller Li/Si molar ratio significantly enhances both the kinetic sorption rate and cyclic stability of the Li4SiO4 sorbent. When the Li/Si molar ratios are 6.2, 4.2, and 3.2 respectively, the maximum adsorption capacities of the three corresponding sorbents are 0.39, 0.36, and 0.29 gCO2/gadsorbent, respectively. At a temperature of 700 °C, the times required for the sorbents to achieve adsorption equilibrium were 15 min, 2 min, and 1.6 min, respectively. Additionally, after 20 adsorption/desorption cycles, the corresponding retention rates of adsorption capacity were 29.4 %, 62.8 %, and 93.9 %, respectively. These results demonstrate the excellent CO2 sorption performance and the significant potential for wide application of this novel Li4SiO4-based high-temperature CO2 sorbent.