Development of High-performance CaO-based CO2 Sorbents Stabilized with Al2O3 or MgO

Two organic templating methods, viz., a Pechini and a resorcinol/formaldehyde (RF) carbon-gel approach were employed to prepare CaO-based, Al2O3- and MgO-stabilized CO2 sorbents. Scanning electron microscopy confirmed the formation of micro- and nanostructured morphologies in the synthetic sorbents. The cyclic CO2 uptake performance of the sorbents was assessed in a thermo-gravimetric analyzer and compared to the reference limestone. It was found that as little as 10 mol% Al3+ was required to obtain cyclically stable CO2 sorbents independent of the synthesis method used. However, a sintering-induced capacity decay of MgO-supported CaO could only be overcome via RF carbon-gel templating approach using at least 20 mol% of Mg2+ for stabilization. X-ray diffraction revealed the formation of mayenite, whereas MgO did not form a solid solution with CaO. The CO2 uptake of the best synthetic sorbent exceeded limestone by more than 300% (after 10 carbonation/calcination cycles).