Simultaneous activity and stability increase of co-precipitated Ni-Al CO₂ methanation catalysts by synergistic effects of Fe and Mn promoters

For CO₂ methanation, the development of highly active and thermostable catalysts is indispensable to cope with the demands of SNG purity in single-pass fixed-bed operation and the exothermal character of the reaction. In this work, a co-precipitated NiAlO_x catalyst with an equimolar Ni/Al ratio is modified by the two promoters Mn and Fe. The combination of both dopants can be used to synthesize highly thermostable catalysts with an enhanced catalytic activity. The activity-stability performance is strongly dependent on the Ni/promoter ratios, with Ni/Mn = 9.5 and Ni/Fe = 7 performing best. Besides doping already during co-precipitation, it is shown that for doping via impregnation the activity-stability performance for a constant Ni/Fe/Mn ratio can be influenced by the preparation procedure. This offers the unique opportunity to target the activity-stability behavior of a co-precipitated NiAlO_x catalyst as required.