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.