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

We investigated direct calcination of four precursors: calcium oxalate (CaC₂O₄; denoted as CaO-1), calcium carbonate (CaCO₃; CaO-2), calcium d-gluconate monohydrate (C₁₂H₂₂CaO₁₄·H₂O; CaO-3), and a commercial calcium carbonate (CaO-4). The effects of precursor selection on CO₂ adsorption performance were systematically compared. CaO-1 exhibited superior initial CO₂ adsorption capacity (0.63 g/g) due to hierarchical porosity, but suffered a 38% capacity loss after 10 cycles from sintering. Al₂O₃ doping (CaO-Al₂O₃, 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: Al₂O₃ 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-Al₂O₃ (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 CO₂ capture with structural durability, providing insights for cost-effective adsorbent optimization.