Effects of preparation methods on the structure and property of Al-stabilized CaO-based sorbents for CO2 capture

CaO-based sorbents are promising candidates for CO2 capture at high temperatures via Ca looping systems. This work aims to examine the effects of preparation methods on the microstructure and performance of Al-stabilized CaO-based sorbents for capturing CO2. Different preparation techniques including wet mixing, co-precipitation and sol-gel auto-combustion synthesis were employed to prepare the Al2O3-stabilized Ca-based sorbents with various mass ratios of components. Changes in CO2 absorbing capacity and stability were clearly observed for the sorbents prepared with different methods. Field scanning electron microscope and N2 adsorption and desorption isotherms analyses showed that the preparation methods tended to impact the morphology and porosity of the sorbents, hence affecting the adsorption capacity. The 27Al magic angle spinning nuclear magnetic resonance spectra of the mixed oxides revealed that the sorbents prepared from different methods all contained the same structural units of tetrahedral Al site (AlO4), but with obviously different intensity and broad shoulder peak. This demonstrated that the micro domain environment of 27Al atoms residing in the lattice could be effectively modified by the doping methods.