HIGHLY-ACTIVE CATALYST OF NIO-ZRO2 MODIFIED WITH H2SO4 FOR ETHYLENE DIMERIZATION

A series of catalysts, NiO-ZrO2/SO42-, for ethylene dimerization were prepared by coprecipitation from a solution of a nickel chloride-zirco nium oxychloride mixture followed by modifying with H2SO4. On the basi s of the results obtained from X-ray diffraction and differential ther mal analysis, the addition of nickel oxide to ZrO2 or modification wit h H2SO4 shifted the transition of ZrO2 from amorphous to a tetragonal phase at higher temperatures due to the interaction between nickel oxi de (or sulfate ion) and ZrO2. Infrared spectra of the catalyst modifie d with H,SO, showed bidentate sulfate ion coordinated to Zr4+ Or Ni2+. NiO-ZrO2 Without sulfate ion was inactive for the ethylene dimerizati on, but NiO-ZrO2/SO42- was found to be very active even at room temper ature. The high catalytic activity of NiO-ZrO2/SO42- was closely corre lated with the increase of acid strength by the inductive effect of su lfate ion. The decrease of catalytic activity above 450 degrees C of e vacuation temperature was due to the structural change from amorphous phase to crystalline and the sintering followed by the decrease of sur face area.