CeO2-Promoted Highly Active Catalyst, NiSO4/CeO2-ZrO2 for Ethylene Dimerization

Abstract

The <TEX>$NiSO_4/CeO_2-ZrO_2 $</TEX>catalysts containing different nickel sulfate and <TEX>$CeO_2$</TEX> contents were prepared by the impregnation method, where support, <TEX>$CeO_2-ZrO_2$</TEX>was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of <TEX>$CeO_2-ZrO_2$</TEX>. The addition of nickel sulfate (or <TEX>$CeO_2$</TEX>) to <TEX>$ZrO_2$</TEX> shifted the phase transition of <TEX>$ZrO_2$</TEX> from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or <TEX>$CeO_2$</TEX>) and <TEX>$ZrO_2$</TEX>. A catalyst (10-<TEX>$NiSO_4/1-CeO_2-ZrO_2$</TEX>) containing 10 wt % <TEX>$NiSO_4$</TEX> and 1 mole % <TEX>$CeO_2$</TEX>, and calcined at <TEX>$600{^{\circ}C}$</TEX> exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of <TEX>$CeO_2$</TEX>was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.