(446k) CO2 Capture Performance of CaO-Based Pellets Stabilized By Metal Oxide Ceramics and Shelled By Mesoporous Glassy Silica, Titania and Zirconia

Calcium oxides (CaO) have been considered as a promising materials for carbon capture at high temperatures due to their high carbon dioxide (CO₂) capacity, low cost, and environmental benignity. Commercialized applications of these materials have been hindered by their severe acitivity loss during the long term performance due to the sintering of the vulnerable CaO particles exposed to high temperatures. In an attempt to overcome these problems, the CaO-based pellet as a core has been synthesized using co-precipitation method doped by zirconium-based ceramic dopants with the range of ratio 5-10% wt. The synthesized CaO-based pellets were then coated by the high thermal resistant mesoporous zirconium dioxide, titanium dioxide or silicon dioxide to provide a reliable protection against the sintering process. The coreshell pellet sorbents were fabricated via the modified sol-gel techniques. The performance and structures of the sorbents have been investigated using TGA, BET, SEM and XRD. The highly crystalline ZrO₂-coated sorbents exhibited a significantly lower capacity decay compared to the uncoated sorbents and natural Cadomin, which could be attributed to the formation of a layered high-temperature-resistant ceramic through the solid-state reaction of the compact and highly crystalline ZrO₂ layer with CaO. The sorbent doped by CaZrO₃ and coated by zirconium dioxide, UF CaO-CaZrO₃@Zr, showed the highest stability among the synthesized sorbents. The activity loss of this sorbent was 20% during 20 cycles of carbonation/oxidation and CO₂ uptake at the first cycle was 10.23 Mole CO₂ per kilogram of sorbent, whereas an activity loss of 68.98 % and 51.2% was obtained for the natural Cadomin and un-coated CaO cores, respectively. The sorbent doped by Al₂Zr₃O₉ and coated by ZrO₂, CaO-Al₂Zr₃O₉@Zr, revealed activity loss of 29.3% during 20 cycles and CO₂ uptake of 10.27 mole per kilogram of sorbent at the first cycle. Moreover, sorbents coated by Silicon dioxide and Titanium dioxides exhibited same performance with uncoated sorbents, which proved that SiO₂ and TiO₂ did not decrease the sintering of CaO particles.