Hydrogen production through methane–steam cyclic redox processes with iron-based metal oxides

Abstract The redox performance of pure iron oxide (Fe 2 O 3 ) and iron oxide modified with ceria (CeO 2 ) and/or zirconia (ZrO 2 ) as an oxygen carrier was investigated for hydrogen (H 2 ) production through a methane–steam redox process. The addition of both CeO 2 and ZrO 2 were found to be a more effective modification of Fe 2 O 3 than the addition CeO 2 or ZrO 2 alone. It was found that the reducibility of Fe 2 O 3 was enhanced by CeO 2 and the thermal stability of Fe 2 O 3 was improved by ZrO 2 . These results, therefore, led to the conclusion of the synergistic effect in the Fe 2 O 3 -CeO 2 -ZrO 2 mixed oxide. As a result, both the redox activity and the thermal stability were significantly improved, and increases in H 2 yield and purity could be maintained by the modification. The redox temperature was found to have a significant effect on redox performance. The production of H 2 was considerably improved when the redox temperature was increased from 650 to 750 °C. The ZrO 2 concentration in Fe 2 O 3 -CeO 2 -ZrO 2 mixed oxide samples was also found to influence performance with the highest H 2 yield observed at a ZrO 2 concentration of 75 wt.%. Although all materials tested showed a reduction in surface area in the first redox cycle, the change in surface area in subsequent cycles was found to be smaller and the yield of H 2 could be maintained at a constant level over a longer period for the mixed oxide containing 75 wt.% ZrO 2 .