The development of effective CaO-based CO₂ sorbents via a sacrificial templating technique

A carbon-based sacrificial templating approach was employed to realize single-pot synthesis of cyclically stable CaO-based CO₂ sorbents. The sacrificial carbonaceous template was formed through resorcinol-formaldehyde polymerization reaction. The resultant sorbents following the thermal decomposition of the carbonaceous template featured an inverse opal-like macrostructure composed of a highly porous nanostructured backbone. In addition to pure CaO, sorbents supported with Al₂O₃, MgO, Y₂O₃, and ZrO₂ were synthesized. SEM and XRD were utilized to characterize the morphology and the chemical composition of the synthetic CO₂ sorbents, respectively. The cyclic CO₂ uptake performance of the synthetic sorbents was assessed by TGA and compared to limestone. All of the synthetic sorbents exhibited an improved CO₂ uptake performance when compared to limestone. The performance enhancement became more pronounced in the case of supported sorbents. The sorbent with the best CO₂ uptake performance was supported by a mixture of Al₂O₃ and Y₂O₃, and exhibited a CO₂ uptake of 0.61 g CO₂/g CaO after 10 cycles of calcination and carbonation under practically relevant operating temperatures, which exceeded the CO₂ uptake of limestone by more than 350%.