Al ₂ O ₃ /MgO‐doped, CaO‐based adsorbents for CO ₂ capture: A performance study

Abstract We investigated direct calcination of four precursors: calcium oxalate (CaC 2 O 4 ; denoted as CaO‐1), calcium carbonate (CaCO 3 ; CaO‐2), calcium d ‐gluconate monohydrate (C 12 H 22 CaO 14 ·H 2 O; CaO‐3), and a commercial calcium carbonate (CaO‐4). The effects of precursor selection on CO 2 adsorption performance were systematically compared. CaO‐1 exhibited superior initial CO 2 adsorption capacity (0.63 g/g) due to hierarchical porosity, but suffered a 38% capacity loss after 10 cycles from sintering. Al 2 O 3 doping (CaO–Al 2 O 3 , 95/5) enhanced capacity and kinetics (0.65 g/g and 0.23 g/g·min −1 , respectively), showing 3% and 43.75% improvements over CaO‐1, respectively, though a degradation of 33.8% occurred after 20 cycles. MgO doping (CaO–MgO, 85/15) achieved exceptional cyclic stability, retaining 93% capacity over 10 cycles (55% improvement vs. CaO‐1) via inherent sintering resistance. Characterization experiments confirmed their structural evolution: Al 2 O 3 stabilized pore networks, while MgO preserved framework integrity. The results demonstrate that precursor engineering and dopant selection critically influence adsorption kinetics versus cyclic stability trade‐offs. Optimal CaO–Al 2 O 3 (95/5) and CaO–MgO (85/15) compositions propose a kinetics–stability decoupling strategy. This dual‐dopant approach addresses calcium looping challenges by balancing rapid CO 2 capture with structural durability, providing insights for cost‐effective adsorbent optimization.

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