The effect of Al2O3 addition on catalytic activities of NiSO4/Al2O3-ZrO2 for acid catalysis

A series of catalysts, NiSO4/Al2O3-ZrO2, for acid catalysis were prepared by the impregnation method, where support, Al2O3-ZrO2 was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and aluminum nitrate solution followed by adding an aqueous ammonia solution. Characterization of prepared catalysts was performed by using Fourier transform infrared, X-ray diffraction, and differential scanning calorimetry and by measuring surface area. No diffraction line of nickel sulfate was observed up to 20 wt%, indicating good dispersion of nickel sulfate on the surface of Al2O3-ZrO2. The addition of nickel sulfate (or Al2O3) to ZrO2 shifted the phase transition of ZrO2 from amorphous to tetragonal to higher temperature because of the interaction between nickel sulfate (or Al2O3) and ZrO2. 10-NiSO4/Al2O3-ZrO2 containing 10 wt% NiSO4 and 5 mol% Al2O3 was calcined at 973 K and exhibited maximum catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The addition of Al2O3 up to 5 mol% gradually enhanced the acidity, thermal property, and catalytic activities of NiSO4/Al2O3-ZrO2 due to the interaction between Al2O3 and ZrO2.