Preparation method study on Fe₂O₃/Al₂O₃ oxygen carrier

Oxygen carrier is one of the essential issues of Chemical Looping Combustion (CLC). In this paper, Fe-based oxygen carriers were prepared by the following seven methods: sol-gel method, co-precipitation method, hydrothermal synthesis method, low-heating solid-state reaction method, mechanical mixing method, combustion synthesis method, and freeze granulation method. The appropriate preparation methods were selected and optimized for preparation process through physical and chemical characterization. Firstly, the hardness tests of the oxygen carriers showed that the oxygen carriers prepared by sol-gel, co-precipitation, mechanical mixing, combustion synthesis, and freeze granulation are harder than others. Then, these oxygen carriers were tested by X-Ray Diffraction (XRD), and Fe₂O₃/Al₂O₃ crystalline phase were found in all these samples. Further XRD analysis showed that the crystallinity and crystallite size of oxygen carriers gradually increased with the increase of calcining time and temperature. The mechanical property, crystal structure and composition of crystalline phase are the most stable when the calcining temperature is 1 200℃. Finally, Temperature Programmed Reduction Reaction (TPR) experiments by the Chemisorption Instrument were carried out to characterize the reactivity of the oxygen carriers, and the activity degree of oxygen carriers was obtained. Following these physicochemical characterizations, the sol-gel method and freeze granulation method were recognized as best for the preparation of Fe₂O₃/Al₂O₃ oxygen carrier.