Phase transition of Fe₂O₃–NiO to NiFe₂O₄ in perovskite catalytic particles for enhanced methane chemical looping reforming-decomposition with CO₂ conversion

This work introduced a perovskite catalytic particle of Fe₂O₃–NiO/La_0.8Sr_0.2FeO₃ as an oxygen carrier and investigated its long-term activity and stability in a novel methane Chemical Looping Reforming-Decomposition (CLRD) process. Carbon dioxide (CO₂) was injected for the oxidation of the reduced catalytic particle and its carbon deposit, resulting in the accelerated production of syngas. The catalytic particle showed over 97% of CH₄ conversion over 60 min and the reduced catalytic particle was partially re-oxidized by both O₂ and CO₂ with the conversion of CO₂ into CO maintaining about 93% over 80 min. The separate phases of Fe₂O₃/NiO were gradually merged to the single crystal phase of NiFe₂O₄ during the calcination of the two metal oxides and the continuous redox reaction cycle. The increased crystallinity can lead to the improvement of both activity and stability due to the enhanced oxygen-carrying capacity. The structure of the catalytic particle was well preserved and its activity has been stable in the long-term CLRD cycle with the combination of CO₂ utilization.