Synthesis of mesoporous MgO–CeO₂ composites with enhanced CO₂ capture rate via controlled combustion

MgO–CeO₂ composites with enhanced sorption rate for CO₂ capture were prepared via a sol-gel combustion method. The effects of water, cerium, and citric acid on the sorption performance were investigated systematically to elucidate the role of components. The cerium content substantially lowered the decomposition temperature by 100 °C and the amount of citric acid affected the propagation rate. Controlled combustion led to different pore structures and CO₂ capture performances, and controlling the amount of citric acid was the most effective way to improve the textural properties and performances. The developed MgO–CeO₂ composites consist of nanoparticles covered with a flat plate, and a small amount of residual carbon from citric acid was also observed in the samples. The optimal MgO–CeO₂ composite using the Ce/Mg molar ratio of 0.05 exhibited a high surface area (333 m²/g) and enhanced CO₂ capture capacity (10.4 wt%) at 30 °C. All the composites showed a fast sorption rate that reached approximately 70% of the capacity within 3 min. The analysis of the CO₂-TPD profiles and XPS spectra indicated that even a relatively small amount of carbonaceous residues after calcinations contributed to retaining more amounts of strong basic sites and consequently resulted in the fast sorption rate. In the cyclic test, the sorption capacity is reasonably stable from the 2nd cycle onwards. The simple preparation via cerium doping and the citric acid-assisted sol-gel combustion can contribute to the development of sorbents for post-combustion as well as pre-combustion CO₂ capture.