Ethylene dimerization over NiSO_4 supported on Fe2O3-promoted ZrO_2 catalyst

摘要

The NiSO_4 supported on Fe_2O_3-promoted ZrO_2 catalysts were prepared by the impregnation method.Fe_2O_3-promoted ZrO_2 was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and iron 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 Fe_2O_3-ZrO_2.The addition of nickel sulfate (or Fe_2O_3) to ZrO_2 shifted the phase transition of ZrO_2 (from amorphous to tetragonal) to higher temperatures because of the interaction between nickel sulfate (or Fe_2O_3) and ZrO_2.15-NiSO_4/5-Fe_2O_3-ZrO_2 containing 15 wt.% NiSO_4 and 5 mol% Fe_2O_3,and calcined at 500 deg C exhibited a maximum catalytic activity for ethylene dimerization.NiSO_4/Fe_2O_3-ZrO_2 catalysts was very effective for ethylene dimerization even at room temperature,but Fe_2O_3-ZrO_2 without NiSO_4 did not exhibit any catalytic activity at all.The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method.The addition of Fe_2O_3 up to 5 mol% enhanced the acidity,surface area,thermal property,and catalytic activities of catalysts gradually,due to the interaction between Fe_2O_3 and ZrO_2 and due to consequent formation of Fe-O-Zr bond.