Redox performance of Fe2O3/Al2O3 oxygen carrier calcined at different temperature in chemical looping process

Abstract

Iron-based oxygen carriers often underwent severe phase segregation in the process of chemical looping, resulting in the reduction of the cyclic performance of oxygen carriers. The phase segregation characteristics of Fe2O3/Al2O3 calcined at different temperature (900 °C, 1100 °C, 1300 °C) were investigated in this study. The obtained samples were recorded as 900-FeAl, 1100-FeAl and 1300-FeAl, respectively. XPS results showed that the surface oxygen vacancies of Fe2O3/Al2O3 increased with the increase of calcination temperature. In the redox cycles, the deactivation rate of the three samples were 5.57% (900-FeAl), 6.99% (1100-FeAl) and 31.69% (1300-FeAl), respectively. After 20 cycles, the 1300-FeAl presented serious surface sintering and the largest enrichment degree of surface Fe (137.05%). It can be inferred that the severe enrichment of surface Fe leads to the serious sintering, which aggravates the deactivation of the 1300-FeAl in cyclic reactions. The low calcination temperature (900 °C, 1100 °C) makes the Fe2O3/Al2O3 exhibit rich pore structure, which generates space barrier for the outward migration of Fe cation and inhibits the phase segregation of Fe2O3/Al2O3. The results of this study are of great significance to understand the phase segregation of iron-based oxygen carriers, and provide guiding value for the synthesis of high-performance iron-based oxygen carriers.