화학공학소재연구정보센터
Energy & Fuels, Vol.34, No.12, 16350-16355, 2020
Activation Mechanism of Fe2O3-Al2O3 Oxygen Carrier in Chemical Looping Combustion
Because of the low cost and easy availability, iron oxides have been widely used in chemical looping combustion. However, pure iron oxides often suffered from a loss of oxygen carrying capacity in redox cycles due to thermal sintering. The redox performance of iron oxides can be improved by the addition of Al2O3 as a support. In this study, the investigation was carried out regarding the activation behavior of a Fe2O3-Al2O3 oxygen carrier in initial cycles. The combined use of different textural and morphological characterization techniques (X-ray diffraction (XRD), X-ray photoelectron spectroscopy XPS, Hg intrusion, and scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS)) was conducted to reveal how microscopic changes triggered the activation of the Fe2O3-Al2O3 sample. It indicated that the activation process of the Fe2O3-Al2O3 sample was caused by the outward migration of Fe cations to the sample surface. A fresh sample presented a surface with a dense and nonporous structure. However, once the sample was activated after the cyclic reactions, Fe cations were enriched on the sample surface in the form of small grains. This leads to enhanced redox activity and increased oxygen carrying capacity.