Unraveling the pore-forming mechanism and thermokinetic behaviors of porous K-Ti co-doped Li4SiO4 pellets for efficient and stable CO2 capture
摘要
The industrial deployment of Li4SiO4-based sorbents for high-temperature CO2 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 Li4SiO4, balancing porosity with mechanical strength in shaped pellets remains a critical challenge. In this work, five porogen-templated K–Ti co-doped Li4SiO4 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 CO2 capture performances were systematically investigated through thermokinetic analysis and multi-scale characterization. Results indicate that the addition of porogen to Li4SiO4-based pellets increased the porosity of the pellets and enhance CO2 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 gCO2/gsorbent 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 CO2 sorption kinetics and mechanical strength, providing a rational strategy for designing robust, high-performance CO2 sorbents for industrial applications.
Graphical Abstract