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

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, H-2/CO, and H-2 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.

Automated summary

Fe2O3/Al2O3 oxygen carriers improved with Mg addition demonstrated excellent reactivity and stability for chemical looping steam reforming of methane (CLSR). The increase in Mg/Al ratio led to decreased lattice oxygen activity but improved methane conversion and CO selectivity.