Correlation between acidic properties of nickel sulfate supported on TiO2-ZrO2 and catalytic activity for ethylene dimerization |
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Authors: | Young Il Pae Si Hoon Lee Jong Rack Sohn |
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Affiliation: | (1) Department of Applied Chemistry, Engineering College Kyungpook National University, Taegu, 702-701, Korea;(2) Department of Chemistry, University of Ulsan, Ulsan, 680-749, Korea |
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Abstract: | A series of catalysts, NiSO4/TiO2-ZrO2, for ethylene dimerization was prepared by the impregnation method using an aqueous solution of nickel sulfate. For NiSO4/TiO2 -ZrO2 sample, no diffraction line of nickel sulfate was observed up to 30 wt%, indicating good dispersion of nickel sulfate on the surface of TiO2-ZrO2. The addition of nickel sulfate to TiO2-ZrO2 shifted the phase transition of TiZrO4 from amorphous to orthorhombic to a higher temperature because of the interaction between nickel sulfate and TiO2-ZrO2. The number of acid sites of NiSO4/TiO2-ZrO2 increased in proportion to the nickel sulfate content up to 20 wt% of NiSO4. Nickel sulfate supported on TiO2-ZrO2 was found to be very active even at room temperature, giving a maximum in both activity and acidity when the catalyst containing 20% NiSO4 was calcined and evacuated at 500°C The asymmetric stretching frequency of the S=O bonds for NiSO4/TiO2-ZrO2 samples was related to the acidic properties and catalytic activity. That is, the higher the frequency, the higher both the number of acid sites and the catalytic activity for ethylene dimerization. |
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Keywords: | ethylene dimerization NiSO4/TiO2-ZrO2 acid strength acidity TiZrO4 compound asymmetric S=O stretching frequency |
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