(395g) Nickel-Iron Catalysts for Low Temperature Dry Reforming of Methane

Dry reforming of methane (DRM) converts two important greenhouse gases, methane and carbon dioxide, in a single reaction to produce syngas. Nickel-based catalysts have been extensively studied for DRM. However, monometallic Ni catalysts deactivate because of coking. We are motivated to include earth-abundant promoter metals to inhibit coke formation and studied series of bimetallic nickel-iron catalysts supported over P-25 TiO₂ at 550ËšC and atmospheric pressure. Ni-Fe catalysts were prepared by wet impregnation and co-precipitation methods. The total metal loading was maintained at 10 wt% with different ratios of Ni/Fe. DRM activity results showed that co-precipitation Ni-Fe/TiO₂ catalyst with Ni/Fe ratio of 3:1 is optimum in terms of CH₄ and CO₂ consumption showing similar reaction rates to Ni/TiO₂ and minimal coke deposits simultaneously. H₂-TPR results showed higher reducibility and enhanced metal and support interaction in Ni-Fe/TiO₂ synthesized by co-precipitation catalysts than that of impregnation catalysts. The activity of CH₄ and CO₂ was higher over Ni-Fe/TiO₂ co-precipitation catalysts than impregnation catalysts. XPS analysis of reduced catalysts showed formation of interacting bimetallic Ni-Fe species over co-precipitation catalysts, while no such Ni-Fe interactive species formed over impregnation catalysts. Spent catalysts which are characterized by TGA-DTG and Raman spectroscopy, showed decrease in coke deposits by 20 times over Ni₃Fe₁/TiO₂ in comparison to monometallic Ni/TiO₂ catalysts. In-situ DRIFTS analysis revealed that DRM reaction intermediate species including hydroxyls (OH^*) and carbonates (COO^*) oxidized coke precursors over Ni-Fe/TiO₂ catalysts.