Abstract: Ni "supported" nano-zirconia catalyst(named as Ni/ZrO₂-AS) was extremely stable for CO₂ reforming of CH₄ to syngas. In the present work, the effects of the Ni loading(5%-32%), reaction temperature(923-1 123 K) and space velocity[GHSV=10⁴-10⁵ mL/(h·g-cat)] were extensively studied. While the catalytic stability of Ni/ZrO₂-AS catalysts seemed not significantly affected by the Ni loading, the increase of the loading up to 10% improved effectively the catalyst activity at 1 030 K. In the reactions over the catalysts with higher Ni loadings, the conversions of the reactants approached their values for thermodynamic equilibrium. The increase of the feed space velocity led to a decrease of the reactant conversions, but to an increase of the space time yield of syngas product. TPO measurement of the carbon deposition showed that every nickel atoms in the catalysts survived dynamically two carbon atoms on the average. TPR/TPD and TEM characterizations revealed that Ni/ZiOr₂-AS catalysts were different in structure from conventional metal catalysts supported on porous oxides; they were nano-composites of size-comparable metallic Ni and ZrO₂ nanocrystals( 10-20 nm). The catalytic stability of Ni catalysts in Ni/ZrO₂-AS system is most probably connected with the nature of the nanoacomposite structures.

Key words: CO₂ reforming of CH₄, Syngas, Nano-zirconia, Ni catalyst, Nanacomposite catalyst