Impact of Promoter Addition on the Regeneration of Ni/Al2O3 Dry Reforming Catalysts

Industrial‐scale reforming of methane is typically carried out with an excess of oxidant to suppress coking of the catalyst. On the other hand, many academic studies on dry reforming employ a CO2/CH4 ratio of unity to quickly observe coking which can be reduced by adding a catalyst promoter. In this work, Ni/Al2O3 catalysts were tested for dry reforming of methane (CO2/CH4=1) with additional regeneration steps to test the resistance against an oxidation treatment. Thereby, we wanted to evaluate catalyst stability for industrial relevance. The effects of three promoters, Cr, Mn and Fe, that differ in their degree of CO2 interaction, are compared. A higher iron loading on Ni/Al2O3 leads to higher stability in dry reforming with lower coke formation. However, the higher the concentration of a promoter with high CO2 affinity, the quicker the catalyst is oxidized during regeneration with CO2. Subsequent reduction of a catalyst oxidized with CO2 leads to considerable sintering in all cases. This sintering induces formation of more coke during dry reforming. On such sintered samples only highly effective promoters in large concentrations still have a noticeable effect compared to unpromoted Ni/Al2O3. Heterogeneous catalysis: Ni/Al2O3 catalysts with different promoters were tested in dry reforming of methane and regenerated under different conditions. This allows for a detailed comparison of promoter effects under different regimes. Ni/Al2O3 with high Fe loadings operates stably for CO2/CH4=1 but quickly deactivates for higher CO2 concentrations.