Enhanced CO₂ Methanation over Solution-Combustion Synthesized Ni/Kaolin Catalysts: The Effect of Fe and La Promotion

Ni-based catalysts supported on kaolin were synthesized via solution combustion synthesis and promoted with Fe and/or La to investigate their catalytic performance in CO₂ methanation. Catalytic tests showed that Fe significantly improved CO₂ conversion from approximately 52% for Ni-catalyst to 83% for Ni2.5Fe_SCS at 300 °C. However, the promotional effect of Fe showed only a weak dependence on its loading, with Ni modification already being achieved at the lowest Fe content. Among all investigated catalysts, the La-promoted sample exhibited the highest CO₂ conversion (85% at 300 °C), owing to the formation of highly dispersed Ni⁰ crystallites, enhanced surface basicity, and strong metal-support interactions. These interactions also effectively suppressed particle sintering during prolonged stability tests. In contrast, simultaneous promotion with Fe and La did not provide additional catalytic enhancement, indicating that the effects of both promoters were not simply additive.