Role of phase in NiMgAl mixed oxide catalysts for CO₂ dry methane reforming (DRM)

Supported Ni catalysts are considered promising for dry methane reforming (DRM) because of their low cost and high activity. However, they suffer from coke formation at elevated reaction temperatures, leading to rapid catalyst deactivation. Here, we developed a synthesis route for highly active and stable nickel-based catalysts for DRM by changing the Mg/Al ratio. Manipulation of the Mg/Al ratio in NiMgAl catalysts induces a change in the phases present, which subsequently leads to enhancement in activity and stability. The highest activity and stability were observed when both spinel and periclase phases were present in the catalysts at Mg/Al ratio of 1.5 (Ni-Mg_1.5AlO_x). Based on X-ray diffraction (XRD), H₂ temperature-programmed reduction (TPR), chemisorption, and UV-Vis-NIR characterizations, as well as CO₂ temperature-programmed desorption (TPD), we found that the co-existence of spinel and periclase phases is associated with changes in Ni reducibility, basicity, and the location of Ni²⁺ species. This work demonstrates how a change in phase in catalysts influences key factors determining activity and stability for the design of active and stable catalysts.