Modification of KNO3 on the reducibility and reactivity of Fe2O3-based oxygen carriers for chemical-looping combustion of methane

摘要

This work presented a comparative study on the Fe2O3-based oxygen carriers modified by different potassium salts (i.e. KNO3, K3PO4, KOH, K2CO3) for chemical looping combustion of methane (CLC with methane). The effect of Al2O3 support on the reactivity of Fe2O3 was also investigated. The Fe2O3-based oxygen carriers were prepared by a co-precipitation method and the potassium salts were added via an incipient wetness impregnation method. The obtained oxygen carriers were characterized by XRD, XPS, H-2-TPR, and CH4-TPR technologies. It was found that the presence of KNO3 could improve the reducibility of the Fe2O3-based oxygen carrier in the surface, resulting in relatively high selectivity towards CO2 during the CLC with methane. The content of KNO3 also affected the reactivity of oxygen carriers, and 10% KNO3/Fe2O3 sample showed the best activity. Moreover, it was also demonstrated that the addition of Al2O3 support into the 10% KNO3/Fe2O3 oxygen carrier could improve its redox performance, and the stability of 10% KNO3/Fe2O3/Al2O3 was proved to be favourable after twenty successive cycles for CLC with methane.