A series of catalysts: NiSO4/TiO2-ZrO2, having different TiO2-ZrO2 compositions, for ethylene dimerization was prepared by the impregnation method using an aqueous solution of nickel sulfate. No diffraction line of nickel sulfate was observed up to 30 wt%, indicating good dispersion of nickel sulfate on the surface of the supported NiSO4 catalysts. The surface area and acidity of TiO2-ZrO2 binary metal oxide increased remarkably compared with the values for single metal oxides, TiO2 or ZrO2. The binary oxide TiO2-ZrO2 calcined above 600 degrees C resulted in the formation of a crystalline orthorhombic phase of ZrTiO4. Therefore, NiSO4/TiO2-ZrO2 calcined at 500 degrees C exhibited a maximum catalytic activity, and then the catalytic activity decreased with the calcination temperature. NiSO4 supported on 50TiO(2)-50ZrO(2) (TiO2/ZrO2 ratio = 1) exhibited the highest catalytic activity for ethylene dimerization among TiO2-ZrO2 binary oxides. The catalytic activities of supported NiSO4 catalysts were correlated with the acidity of catalysts measured by the ammonia chemisorption method, regardless of the kind of support (Ti02, ZrO2, or TiO2-ZrO2). (c) 2007 Elsevier B.V. All rights reserved.