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Description
Nickel–iron catalysts supported on alumina are promising systems for the dry reforming of methane (DRM), combining high activity with relatively low cost and improved resistance to carbon deposition. In this work, the structural evolution of Ni–Fe/Al2O3 catalysts was studied under DRM conditions using SEM–EDX, XRD, and ferromagnetic resonance (FMR). Calcination produced NiO and Fe2O3/Fe3O4, while reduction yielded metallic Ni, Fe, and Ni–Fe alloys. Strong metal–support interactions led to spinel phases (NiAl2O4, FeAl2O4), acting as reservoirs for active metals. Under DRM conditions (700–900 °C), Ni–Fe alloys dominated, with spinel stabilizing the catalyst. Dynamic redox cycles between Fe2+/Fe3+ enhance oxygen mobility and carbon gasification. At 700–900 °C (typical DRM conditions), equilibrium favors Ni–Fe alloys + residual spinel phases. Ni–Fe alloys are catalytically active, while Fe-containing oxides act as oxygen carriers, suppressing coke accumulation. Ni provides high intrinsic activity for CH4 activation; Fe dilutes Ni assemblies, reducing coking. Balanced H2/CO ratios (~1.0) are achievable, but Fe-rich alloys can promote the Boudouard reaction (2CO→C+CO2). Fe alloying and the formation of partially reducible spinel phases increase resistance to sintering and carbon deposition. These findings highlight the importance of balancing Ni–Fe alloy phases and spinel structures for long-term catalyst stability and efficient DRM performance.
