Enhancing sorption kinetics of the ternary alkali nitrate salts‐promoted MgO sorbents via sorbent activation for post‐combustion carbon capture from low CO 2 concentration stream

BACKGROUND MgO‐based sorbents offer high theoretical CO 2 capacity but are constrained in practical applications by sluggish sorption kinetics, prolonged induction periods, and poor performance under the low CO 2 concentration typical of flue gas. This study proposes a mild activation strategy to reduce the nucleation barrier for MgCO 3 formation and investigates its effectiveness together with reactor operating conditions using a simulated flue gas stream containing 15% CO 2 . RESULTS The fresh 9 mol% (Li 0.18 Na 0.52 K 0.30 )NO 3 ‐MgO sorbent exhibited slow carbonation kinetics, requiring 74.2 min to reach its peak sorption rate of 0.0423 mmol/g·min and achieving 7.58 mmol/g at 280 °C after 4 h. Activation at 240 °C for 0.5 h shortened the time to peak sorption to 8.1 min, increased the peak sorption rate to 0.0784 mmol/g·min, thereby enhancing the CO 2 uptake to 9.46 mmol/g. Effective regeneration required temperatures above 320 °C, with non‐isothermal operation achieving >90% desorption efficiency at 340 °C. Although activation substantially improved intrinsic sorption kinetics, high CO 2 removal efficiency was only achieved when sufficient gas–solid contact time was provided. At a weight hourly space velocity (WHSV) of 1.7 mL/g·min after sorption at 280 °C for 4 h, the activated sorbent achieved 81.9% CO 2 removal efficiency. The activated sorbent maintained an average CO 2 removal efficiency of 81.35% over 10 cycles, with each sorption cycle lasting for 1.5 h at 280 °C. CONCLUSION Activation improves the intrinsic sorption kinetics, while lowering the WHSV translates these kinetic improvements into high CO 2 removal efficiency.