Optimizing the Sulfur-Resistance and Activity of Perovskite Oxygen Carrier for Chemical Looping Dry Reforming of Methane

Perovskite oxides has been attracted much attention as high-performance oxygen carriers for chemical looping reforming of methane, but they are easily inactivated by the presence of trace H2S. Here, we propose to modulate both the activity and resistance to sulfur poisoning by dual substitution of Mo and Ni ions with the Fe-sites of LaFeO3 perovskite. It is found that partial substitution of Ni for Fe substantially improves the activity of LaFeO3 perovskite, while Ni particles prefer to grow and react with H2S during the long-term successive redox process, resulting in the deactivation of oxygen carriers. With the presence of Mo in LaNi0.05Fe0.95O3−σ perovskite, H2S preferentially reacts with Mo to generate MoS2, and then the CO2 oxidation can regenerate Mo via removing sulfur. In addition, Mo can inhibit the accumulation and growth of Ni, which helps to improve the redox stability of oxygen carriers. The LaNi0.05Mo0.07Fe0.88O3−σ oxygen carrier exhibits stable and excellent performance, with the CH4 conversion higher than 90% during the 50 redox cycles in the presence of 50 ppm H2S at 800 °C. This work highlights a synergistic effect in the perovskite oxides induced by dual substitution of different cations for the development of high-performance oxygen carriers with excellent sulfur tolerance.