Unraveling the pore-forming mechanism and thermokinetic behaviors of porous K-Ti co-doped Li4SiO4 pellets for efficient and stable CO2 capture

Abstract The industrial deployment of Li 4 SiO 4 -based sorbents for high-temperature CO 2 capture is often hindered by densification and diffusion limitations derived from particle shaping process. While K–Ti co-doping has been demonstrated to enhance intrinsic reactivity of Li 4 SiO 4 , balancing porosity with mechanical strength in shaped pellets remains a critical challenge. In this work, five porogen-templated K–Ti co-doped Li 4 SiO 4 pellets were synthesized via extrusion–spheronization using typical porogens: α-cellulose fiber (CF), graphite (C), polyvinyl alcohol (PVA), and polyethylene (PE). The impact of diverse porogen on microstructural evolution, pore structure, and CO 2 capture performances were systematically investigated through thermokinetic analysis and multi-scale characterization. Results indicate that the addition of porogen to Li 4 SiO 4 -based pellets increased the porosity of the pellets and enhance CO 2 capture perfomance. The organic polymeric templates facilitate the formation of a highly interconnected mesoporous structure, yielding a significant increase in specific surface area compared to the porogen-free sample. Among these sorbents, CF- and PE-templated pellets demonstrated exceptional cyclic stability, maintaining a high capacity of > 0.25 g CO2 /g sorbent over an extended 340 sorption–desorption cycle test. Notably, the CF-templated pellets successfully resolved the strength-kinetics trade-off by sustaining this capacity while exhibiting superior mechanical properties, including great compressive strength (15.9 N) and attrition resistance (< 5 wt% loss after 2000 rotations). This study demonstrates how tailored porosity can optimize the balance between CO 2 sorption kinetics and mechanical strength, providing a rational strategy for designing robust, high-performance CO 2 sorbents for industrial applications. Graphical Abstract