Tuning the metal-support interaction in Ni/MgAl2O4 catalyst for carbon dioxide methanation reaction

This study investigates the influence of metal–support interaction (MSI) on the performance of Ni/MgAl₂O₄ catalysts for CO₂ methanation. Modulating MSI in NiMgAl₂O₄ is shown to be an effective approach to enhance catalytic activity and CH₄ selectivity. A series of 15 wt% Ni/MgAl₂O₄ catalysts were synthesized by varying the calcination temperature (300–1000 °C) to tailor Ni particle size, dispersion, Ni–Mg–Al oxide formation, and active site characteristics. Catalysts were benchmarked against Ni/MgO and Ni/Al₂O₃ calcined at 850 °C. Textural analysis (N₂ adsorption–desorption) revealed a decline in surface area with increasing calcination temperature but an optimal texture at 850 °C. Characterization by H₂-TPR, XRD, UV–vis, TEM, and XPS confirmed progressive MSI strengthening, the development of Ni–Mg–Al mixed oxides and NiAl₂O₄ phases, smaller NiO crystallites, and partial Ni incorporation into the MgAl₂O₄ lattice at higher temperatures. In-situ DRIFTS identified temperature-dependent surface intermediates during CO₂ methanation over NiMgAl850: carbonate/bicarbonate species dominated below 200 °C, while formate and adsorbed CO correlated with CH₄ formation above 200 °C. Among the series, NiMgAl850 exhibited the smallest NiO crystallite size (∼5.6 nm), well-balanced MSI, and optimal surface basicity, delivering the highest CO₂ conversion and CH₄ selectivity. Post-reaction XRD, Raman, and spent-catalyst analyses confirmed minimal sintering, coking, and phase transformation (400–550 °C). Compared with Ni/MgO and Ni/Al₂O₃, the Ni–MgAl₂O₄ interface provides a balanced MSI environment, avoiding excessively strong Ni–MgO or NiAl₂O₄ interactions, thus ensuring stable and active CO₂ methanation performance.