A Design of Experiment‐Driven Optimization of NiMnAl Mixed Metal Oxide Catalysts for CO ₂ Methanation

Abstract Power‐to‐gas technologies, including CO 2 methanation, offer a promising strategy for mitigating anthropogenic climate change. Nickel‐based mixed metal oxide catalysts have demonstrated high activity, selectivity and stability in this challenging reaction in recent years. This study investigates the effects of synthesis parameters on the structure, activation, and reaction behavior of NiMnAl mixed metal oxide (MMO) catalysts. A Design of Experiment approach was employed to systematically vary the calcination temperature (500–950 °C), pH (8–10), and aging time (1–30 h) during synthesis by coprecipitation, resulting in the synthesis and testing of approximately 35 catalysts. The calcination temperature determines the catalyst structure, with metastable NiAl phases forming up to 650 °C and spinel phases forming above 800 °C. Notably, the spinel NiMnAl MMO catalysts exhibit superior performance, achieving approximately 60% higher methane formation rates per gram Ni of the catalyst compared to a supported industrial methanation reference catalyst (SPP2080‐IMRC). Comprehensive characterization using XRD, elemental analysis, N 2 physisorption, TPR, CO 2 ‐TPD, N 2 O chemisorption, and STEM‐EDXS provide insights into the catalysts' properties and activity.