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 (Sr 0.5 La 0.5 ) 2 Fe 0.625 Cu 0.375 O 4 functions as a redox catalyst and/or a CO 2 sorbent to enable three syngas-generation pathways from methane and CO 2 or CO 2 -containing flue gas with tunable syngas composition: (i) sorption-looping dry reforming of methane (SLDRM) using O 2 -free CO 2; (ii) SLDRM coupled with redox reactions under extended cycle duration; and (iii) integrated SLDRM/partial oxidation (POx) using O 2 and CO 2 -containing flue gas. In the O 2 -containing mode, flue-gas CO 2 is captured and utilized in SLDRM while residual O 2 drives methane POx, partially offsetting the SLDRM endotherm. Phase-dependent behavior under reaction conditions explains this flexibility: (Sr 0.5 La 0.5 ) 2 Fe 0.625 Cu 0.375 O 4 converts to SrLaFeO 4 and Cu/SrO components, where Cu/SrO captures CO 2 and SrLaFeO 4 is redox-active. In contrast, the perovskite Sr 0.5 La 0.5 Fe 0.625 Cu 0.375 O 3, 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.