Acidic properties of nickel sulfate supported on TiO 2–ZrO 2 and catalytic activity for acid catalysis

Abstract

A series of catalysts, NiSO 4/TiO 2-ZrO 2, was prepared by the impregnation method using an aqueous solution of nickel sulfate. Calcination at 300–600 °C of co-precipitated Ti(OH) 4–Zr(OH) 4 resulted in the formation of an amorphous phase and further heating at 700 °C and above resulted in the formation of crystalline ZrTiO 4 compound. For NiSO 4/TiO 2-ZrO 2 sample, no diffraction line of nickel sulfate was observed up to 30 wt.%, indicating good dispersion of nickel sulfate on the surface of TiO 2–ZrO 2. The addition of nickel sulfate to TiO 2–ZrO 2 shifted the phase transition of ZrTiO 4 from amorphous to orthorhombic to higher temperature because of the interaction between nickel sulfate and ZrTiO 4, and the acid amount of NiSO 4/TiO 2-ZrO 2 increased in proportion to the nickel sulfate content up to 20 wt.% of NiSO 4. The high catalytic activity of NiSO 4/TiO 2-ZrO 2 was related to the increases of acid amount and acid strength due to the addition of NiSO 4. The catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation, were correlated with the acid amounts of catalysts measured by on ammonia chemisorption method. The asymmetric stretching frequency of the SO bonds for NiSO 4/TiO 2-ZrO 2 samples was related to the acidic properties and to the catalytic activity for acid catalysis. That is, the higher the frequency, the larger the acid amount and catalytic activities for 2-propanol dehydration and cumene dealkylation.