Effect of preparation of iron-based oxygen carrier on carbon deposition during chemical looping reforming

Iron-based perovskite oxygen carriers (OC) play a crucial role in methane chemical looping reforming and can be used for partial oxidation of methane to produce syngas with a 2:1 H 2 /CO ratio. However, methane cracking inevitably leads to carbon deposition on the OC, causing deactivation. In order to elucidate the carbon deposition behavior, this study systematically investigates the effects of La/Fe ratios, carriers, and preparation methods on carbon deposition. The results show that a higher La/Fe ratio directly accelerates CH 4 decomposition into high-temperature carbon (filamentous and graphite carbon). Optimizing the La/Fe ratio (0.75) enhances framework stability and balances oxygen vacancies, which is beneficial for mitigating carbon deposition. Al 2 O 3 addition promotes the formation of the La-MP structure, exhibiting the lowest total carbon deposition (8.38 mmol/gOC) and effectively suppressing the formation of graphite carbon. However, no carrier, MgAl 2 O 4 and SiO 2 addition promote the growth of filamentous and graphite carbon. Among the preparation methods evaluated, co-precipitation method exhibits superior performance by improving the dispersion of the perovskite phase. Compared to the sol–gel method, co-precipitation method suppresses filamentous and graphitic carbon formation, reducing total carbon deposition by 40 %. This study reveals a structure–property relationship described as “composition/structure—methane cracking—carbon deposition type—stable carbon enrichment,” indicating that carbon deposition deactivation depends on the selective formation and stabilization evolution of carbon species, rather than solely on the total amount of carbon deposited. This provides new insights for designing highly active, carbon deposition-resistant iron-based perovskite OCs.