CeO₂-Promoted Highly Active Catalyst, NiSO₄/CeO₂-ZrO₂ for Ethylene Dimerization

摘要

The NiSO₄/CeO₂-ZrO₂ catalysts containing different nickel sulfate and CeO₂ contents were prepared by the impregnation method, where support, CeO₂-ZrO₂ was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of CeO₂-ZrO₂. The addition of nickel sulfate (or CeO₂) to ZrO₂ shifted the phase transition of ZrO₂ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or CeO₂) and ZrO₂. A catalyst (10-NiSO₄/1-CeO₂-ZrO₂) containing 10 wt % NiSO₄ and 1 mole % CeO₂, and calcined at 600 ∑C exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of CeO₂ was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.