Preparation of CaO–Al2O3 sorbent and CO2 capture performance at high temperature

CaO–Al2O3 sorbents were synthesized through the citrate preparation route using citric acid, aluminum nitrate and CaCO3 as raw materials. In the final calcination step, a four-step heating mode, which might favor the formation of porous structure, was adopted to activate sorbents instead of the traditional one step activation procedure. The synthetic CaO–Al2O3 sorbents were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Micrometrics ASAP 2010 apparatus. The CO2 capture capacity and long-term stability of the synthetic CaO–Al2O3 sorbent were tested with a thermogravimetric analyzer (TGA) over 100 carbonation and calcination cycles. Furthermore, the formation mechanism of the inert support substance in the prepared CaO–Al2O3 sorbent was analyzed. It was found that the synthetic CaO–Al2O3 sorbent with 9% Al2O3 additive had a higher specific surface area (958 m2/g) and larger pore volume (0.85 cm3/g), and the CO2 capture capacity, reaction kinetics and long-term cycle stability were improved significantly when compared with the performance of untreated CaO.