Calcium-based sorbent doped with attapulgite for CO2 capture

• The optimal doping ratio of attapulgite to calcined limestone was 15 wt.% in hydration.
• The modified sorbent displayed much better CO2 capture performance than the limestone.
• Excellent microstructure of the modified sorbent was created by doping attapulgite.
• Ca2SiO4, Al2O3 and Ca3Al10O18 distributed in the sorbent enhanced the sintering-resistant.

Attempt to enhance CO2 uptake of calcium based sorbents by doping limestone with attapulgite was made and successfully achieved its effectiveness. The appropriate doping mode and optimal ratio were identified. The cyclic carbonation behavior was conducted under conditions of different carbonation temperature, calcination temperature, CO2 partial pressure in carbonation and calcination atmosphere. Microstructure and compositions of sorbents were analyzed to serve as a supplement to the studies. Results show that the optimal doping ratio of attapulgite to calcined limestone was 15 wt.% in the process of hydration. The doped sorbent displayed much better CO2 capture performance than the natural limestone by 128% increase after 20 cycles under the same condition (calcination at 950 °C in 100% CO2 and carbonation at 700 °C in 15% CO2/85%N2). Excellent microstructure of the modified sorbent was created by doping attapulgite enabling higher CO2 capture capacity. Ca2SiO4, Al2O3 and Ca3Al10O18 distributed in the sorbent by XRD analysis enhanced its sintering-resistant leading to slow decrease in CO2 capture capacity during multiple cycles.