CaO‐Based CO 2 Sorbents Effectively Stabilized by Metal Oxides

Calcium looping (i.e., CO 2 capture by CaO) is a promising second‐generation CO 2 capture technology. CaO, derived from naturally occurring limestone, offers an inexpensive solution, but due to the harsh operating conditions of the process, limestone‐derived sorbents undergo a rapid capacity decay induced by the sintering of CaCO 3 . Here, we report a Pechini method to synthesize cyclically stable, CaO‐based CO 2 sorbents with a high CO 2 uptake capacity. The sorbents synthesized feature compositional homogeneity in combination with a nanostructured and highly porous morphology. The presence of a single (Al 2 O 3 or Y 2 O 3 ) or bimetal oxide (Al 2 O 3 ‐Y 2 O 3 ) provides cyclic stability, except for MgO which undergoes a significant increase in its particle size with the cycle number. We also demonstrate a direct relationship between the CO 2 uptake and the morphology of the synthesized sorbents. After 30 cycles of calcination and carbonation, the best performing sorbent, containing an equimolar mixture of Al 2 O 3 and Y 2 O 3 , exhibits a CO 2 uptake capacity of 8.7 mmol CO 2  g −1 sorbent, which is approximately 360 % higher than that of the reference limestone.