Microwave-optimized synthesis of calcium particles for enhanced CO2 capture and cyclic stability

Overview & Synopsis

Calcium-based solids are promising candidates for CO2 capture due to their high reactivity and availability. However, their low cyclic stability due to particle agglomeration remains a major challenge. In this study, calcium oxide, CaO, particles were prepared via thermal decomposition using calcium hydroxide, Ca(OH)2, as precursor. Ca(OH)2 particles were synthesized using a microwaveassisted method as the primary heating source to optimize particle size, and decrease their agglomeration. The influence of synthesis parameters, including pH, precursor concentration, and temperature, on particle size (nm) and precipitation yield (%) were evaluated using an experimental design and response surface analysis. It was observed that controlling pH and temperature significantly reduce particle size, while only pH affected precipitation yield. The results also provided insights into the effect of microwave irradiation on the pre-nucleation stage, which influences particle growth and size. Then, controlled synthesis of Ca(OH)2 was crucial for achieving the structural properties of CaO. The decrease of the CaO particle size led to a larger external surface area and improved interparticle volume. The better controlled structure also significantly improved the CO2 capture performance by 30 %, including enhanced cyclic stability and kinetics, due to improved gas diffusion into the CaO. Notably, CaO-small achieved a remarkable CO2 cyclability of 90 % under high temperature (650 °C, 1 bar) and high-pressure (25 °C, 8 bar) conditions in the first three cycles, offering a new strategy to develop CaO-based materials. These findings suggest that microwave irradiation may be a viable method to optimize calcium-based materials for CO2 capture, offering enhanced surface area, better resistance to sintering, and cyclic stability.