Enhanced cyclic redox reactivity of Fe2O3/Al2O3 by Sr doping for Chemical-Looping combustion of solid fuels

[Display omitted] •The redox activity of Sr-doped Fe2O3/Al2O3 was studied in CLC of solid fuels.•The anti-sintering ability of Fe2O3/Al2O3 was effectively increased by adding Sr.•Sr dopant suppressed the outward diffusion of Fe cations in Fe2O3/Al2O3. Aiming at the problems of low redox activity and easy sintering deactivation of iron-based oxygen carriers (OCs), Sr was used to modify Fe2O3/Al2O3 in chemical looping combustion (CLC) of solid fuels. The Sr doped Fe2O3/Al2O3 possessed high fuel combustion reactivity with different solid fuels (coal, coal char and biomass). During consecutive cycles, high cycling durability and morphological preservation were observed for Sr doped Fe2O3/Al2O3, signifying that the addition of strontium effectively enhanced the anti-sintering ability and inhibited the phase segregation of Fe2O3/Al2O3 during cyclic reactions. By comparing the coal char combustion reactivity of Fe2O3/Al2O3 samples doped with different SrO content (1 wt%, 5 wt% and 10 wt%), the optimum additive amount of SrO was 5 wt%. In addition, the characterization analysis proved that the Sr dopant suppressed the outward diffusion of Fe cations and maintained the surface micro-morphology of Fe2O3/Al2O3 in the process of CLC. This study presented important guiding principle and strategy for the synthesis of iron-based OCs with high cyclic redox reactivity in the CLC of solid fuels.