Catalytic performance of iron-promoted nickel-based ordered mesoporous alumina FeNiAl catalysts in dry reforming of methane

Abstract

The technologic route of efficiently converting methane into higher-value liquid-phase products that are easily transported have led to an increased industrial interest in the dry reforming of methane (DRM) to produce syngas. However, the nonprecious-metal catalysts suffer from a stability issue caused by coke formation. In this work, by evaporation-induced self-assembly (EISA) method, secondary metals (M = Fe, Co, or Cu) were doped into Ni-based ordered mesoporous alumina catalyst (MNiAl). The difference in catalytic behaviors for these catalysts in DRM could be explained in term of carbon deposition. CuNiAl catalyst displayed the lowest reactivity and poor stability, while FeNiAl was catalytically active. The influence of iron content (molar ratio of Fe/Ni ranging from 0.3 to 0.9) on the catalytic performance for x-FeNiAl were further investigated. Increasing the amount of iron in the catalysts affected both the chemical and activity properties. All x-FeNiAl catalysts showed high surface area and ordered mesoporous structure at Fe/Ni = 0–0.7, whereas the mesoporous structure was destroyed at high Fe/Ni molar ratio (=0.9). Iron displayed a positive role in nickel-based catalysts for DRM by virtue of the formation of FeNi3 alloy species during the reduction treatment. 0.7-FeNiAl catalyst was the most active for reforming with regard to the initial activity. By comparison of STEM-EDX, XPS and XRD results for reduced and spent 0.7-FeNiAl catalysts, the deactivation after 24 h DRM reaction was associated with the dealloying of FeNi3 under reforming conditions, rather than change in porous structure and sintering of the active metal. This study demonstrated the importance in manipulating the stability of FeNi3 that are relevant to DRM conditions.