Synergistic Role of ZrO₂ Promoter and Ni–NiO– ZrO₂ Networks in Improving Ni Catalysts for Dry Methane Reforming at Low Temperature

This study investigates the development of Ni-based catalysts for low-temperature dry methane reforming (DMR) at 550 °C. The catalysts were prepared by dispersing Ni on γ-Al2O3 modified with 9 wt% MgO and 1 wt% ZrO2, while 10 wt% Ni–x wt% ZrO2 promoters (0, 1, and 3 wt%) were introduced using the incipient wetness impregnation method. A Ni–NiO–ZrO2 surface network was generated on the 10 wt% Ni–3 wt% ZrO2 catalyst via an ammonia vapor–assisted impregnation route. The ZrO2 promoter strengthened the metal–support interaction, which increased the total amount of reducible Ni while shifting the reduction to higher temperatures. This modification also promoted CO2 activation relative to CH4, thereby enhancing the RWGS pathway and lowering the H2/CO ratio. In contrast, the Ni–NiO–ZrO2 network formed through the ammonia-assisted method increased the concentration of surface-accessible Ni, reduced excessive coverage by ZrO2, and significantly improved oxygen mobility. These features facilitated continuous oxygen transfer, enhanced coke oxidation, and ensured a more balanced activation of both reactants. Overall, the combined structural and functional synergies achieved through promoter optimization and the ammonia vapor–assisted preparation method resulted in superior catalytic activity and selectivity for DMR at 550 °C.