Silica Modified Alumina As Supports of Fe2O3 with High Performance in Chemical Looping Combustion of Methane

Fe2O3/Al2O3 oxygen carriers (OCs) are considered to be promising due to their high reactivity in chemical looping combustion (CLC). However, iron species and supports suffered from severe sintering, leading to the deactivation of this OC during multiple redox reaction. In this work, a series of silica modified alumina were used as supports of Fe2O3 and found that the OC with the addition of 5% Si (Si-5) exhibited the highest performance for CLC of CH4 during 60 redox cycles. Si was discovered to be incorporated into Al rich coordination environment and the formed Si-O-Al structure inhibited phase transformation of gamma-Al2O3 to alpha-Al2O3, which stabilized the support with high specific surface area. This led to the best dispersion of iron oxides during reaction (77%), confirmed by the formation of the highly dispersed epsilon-Fe2O3 phase identified in the reaction, which resulted in the largest amount of active FeAl2O4 (47%) in the reduction step.