Abstract: The catalytic activity and stability of Ni supported on γ-Al₂O₃, TiO₂, SiO₂, conventional ZrO₂-CP, and nano-ZrO₂-AS(15-20 nm) were comparatively studied for CO₂ reforming of CH₄ to synthesis gas. The Ni loading in these catalysts was limited to 5%(mass fraction) of the supports, and the reaction was performed in a fixed bed flow microreactor at 1030 K with GHSV=2.4×10⁴ mL/(h·g cat). The initial CH₄ conversions of the catalysts are in the order of Ni/ γ-Al₂O₃>Ni/TiO₂>Ni/ZrO₂-CP> Ni/ZrO₂-AS > Ni/SiO₂ . Ni catalysts supported on γ-Al₂O₃, TiO₂, ZrO₂-CP and SiO₂ deactivated rapidly in less than 50h TOS, but Ni/ZrO₂-AS catalyst showed no deactivation for longer than 200h. The pure ZrO₂-AS also showed a catalytic activity for the reaction and no loss of the activity was observed during₅₀ h on stream at 1073 K. TPOmeasurements demonstrated that carbon deposition on the Ni/ZrO₂-AS catalyst was much less and was eliminated at lower temperature than those over the other catalysts. Explanation for the excellent stability of Ni/ZrO₂-AS catalyst was given based on the present data. It is suggested that Ni/ZrO₂-AS can be better expressed as a nano composite of the Ni and ZrO₂-AS, and high percentage of the metal-support perimeter in the composite seems crucial for the long stability of the catalyst.

Key words: Carbon dioxide, Methane reforming, Synthesis gas, Ni catalyst, Nano-zirconia catalyst, Support effect