Enhanced cyclic redox reactivity of hematite via Sr doping in chemical looping combustion

Aiming at the problems of low redox activity and easy sintering deactivation of hematite, Sr was used to modify hematite in chemical looping combustion (CLC). The results showed that a low concentration (1 wt%) of Sr dopant could significantly improve the redox activity and cyclic stability of hematite. During the successive redox cycles, the surface sintering was not occurred for the Sr-doped hematite samples, indicating that Sr could significantly intensify the sintering resistance of hematite in CLC. In the first redox cycle, the oxygen carrying capacity of the Sr-doped hematite samples followed the sequence: 10Sr-HM (3.32%) > 5Sr-HM (3.20%) > 1SrHM (2.11%). By comparing the redox performance of hematite samples doped with different SrO content, 5 wt% is the best addition ratio of SrO dopant. The results of successive 50 cycles indicated that the hematite sample doped with 5 wt% SrO exhibited very high cyclic stability. For the 5Sr-HM, the CH4 conversion and CO2 selectivity was about 90% and 100%, respectively. In addition, the effect of calcination temperature (950 degrees C, 1050 degrees C, 1150 degrees C) on the redox performance of Sr-doped hematite was also considered. The results indicated that the Sr-doped hematite presented high redox activity after high temperature calcination.

Automated summary

By doping with Sr, the redox activity and cyclic stability of hematite in chemical looping combustion (CLC) were significantly improved. Sr could enhance the sintering resistance of hematite and 5 wt% SrO doping was found to be the optimal ratio. High temperature calcination also enhanced the redox activity of Sr-doped hematite.