High temperature capture of CO2 on Li4SiO4 sorbents via a simple dry ball-milling coupled with K2CO3 physical addition

The reversible CO₂ absorption/desorption of lithium orthosilicate (Li₄SiO₄) sorbents holds potential for high temperature capture of CO₂ from hot flue gases, sorption-enhanced reforming and solar thermochemical energy storage. In this study, we have prepared a series of Li₄SiO₄ sorbents using a combination of K₂CO₃ addition and dry ball-milling procedure to improve the relatively slow kinetics under low CO₂ partial pressure conditions. The synergistic effects of dry ball-milling and K₂CO₃ addition on the intrinsic properties of Li₄SiO₄ sorbents were explored by thermogravimetric analysis and structural characterizations. Thermogravimetric analysis indicate that the highest CO₂ uptakes were achieved with dry ball-milling combined with K₂CO₃ physical addition. The structural characterizations further reveal that this sorbent (P-3K-1.5 M) had the smallest crystallite/particle size, largest surface area, and highest availability of surface alkaline-sites. The kinetics analysis also demonstrates that P-3K-1.5 M exhibited the fastest sorption kinetics during a double process. Additionally, P-3K-1.5 M maintained a high capacity over 10 sorption/desorption cycles. Therefore, this synthesis technique, which is simple, cost-effective, and easily scalable, shows great promise for high-temperature CO₂ capture.