Enhanced Fe2O3/Al2O3 Oxygen Carriers for Chemical Looping Steam Reforming of Methane with Different Mg Ratios

Abstract

Fe2O3/Al2O3 oxygen carriers improved with Mg addition were used for the chemical looping steam reforming of methane (CLSR) in a lab-scale fluidized bed reactor. The oxygen carrier with a (Mg+Fe)/Al molar ratio of 0.5 exhibited the most promising reactivity and stability as CO selectivity, CH4 conversion, H2/CO, and H2 yield remained at 96%, 82%, around 2, and 0.75 mmol/g oxygen carrier, respectively, after the 15th cycle, and only the Mg–Fe–Al–O spinel appeared after 50 cycles. According to characterization, the Mg–Fe–Al interaction was the root cause of performance differences. With the increase of the Mg/Al ratio, the reacted oxygen carriers possessed a decreased Fe2+/Fe3+ and exhibited better lattice oxygen activity, but depressed the CH4 conversion and CO selectivity during the CH4 reduction stage. The oxygen carrier with low-lattice-oxygen activity followed the indirect mechanism with C as the intermediate product, leading to high CH4 conversion and CO selectivity.