One-Step Synthesis of Highly Active and Stable Ni–ZrO_x for Dry Reforming of Methane

A series of Ni–Zr catalysts with different Ni loadings were prepared by a novel one-step urea hydrolysis method and compared to the 10Ni/ZrO₂ catalyst prepared by the ethanol impregnation method. The catalysts were tested in dry reforming of methane (DRM) at 750 °C with a mixed flow of CH₄/CO₂/Ar = 10:10:80 and GHSV = 24,000 h^–1. The materials were characterized by means of N₂ adsorption–desorption, X-ray diffraction, temperature-programmed reduction by H₂, temperature-programmed desorption of CO₂, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis coupled with mass spectrometry. 10Ni–Zr and 15Ni–Zr catalysts prepared by the one-step method exhibited higher activity, long-run stability, and selectivity of H₂/CO compared to 10Ni/ZrO₂ catalysts. This could be ascribed to the smaller Ni crystallite size, increased specific surface area, and enhanced weak- and medium-strength basic sites over reduced 10Ni–Zr and 15Ni–Zr catalysts. The 10Ni–Zr and 15Ni–Zr catalysts demonstrated the suppression of metallic nickel sintering because of the formation of NiO–ZrO₂ solid solution, leading to the stronger interaction between Ni and the ZrO₂ matrix. Moreover, stability enhancement for these catalysts was possibly linked to a higher amount of adsorbed oxygen species, as confirmed by XPS.