Chemical-Looping Reforming of Methane with Tunable CO ₂ Utilization over Ruddlesden–Popper and Perovskite Carriers

This work demonstrates that the Ruddlesden–Popper (RP) structured (Sr0.5La0.5)2Fe0.625Cu0.375O4 functions as a redox catalyst and/or a CO2 sorbent to enable three syngas-generation pathways from methane and CO2 or CO2-containing flue gas with tunable syngas composition: (i) sorption-looping dry reforming of methane (SLDRM) using O2-free CO2; (ii) SLDRM coupled with redox reactions under extended cycle duration; and (iii) integrated SLDRM/partial oxidation (POx) using O2 and CO2-containing flue gas. In the O2-containing mode, flue-gas CO2 is captured and utilized in SLDRM while residual O2 drives methane POx, partially offsetting the SLDRM endotherm. Phase-dependent behavior under reaction conditions explains this flexibility: (Sr0.5La0.5)2Fe0.625Cu0.375O4 converts to SrLaFeO4 and Cu/SrO components, where Cu/SrO captures CO2 and SrLaFeO4 is redox-active. In contrast, the perovskite Sr0.5La0.5Fe0.625Cu0.375O3, without excess Sr, acts primarily as an oxygen carrier, indicating that the as-synthesized structure/composition governs the reaction pathway, syngas ratio, and suitable process configuration.