High catalytic activity of [formula omitted] for ethylene dimerization

Abstract

A series of catalysts, NiOTiO 2 SO 4 2− , for ethylene dimerization were prepared by coprecipitation followed by treatment with H 2SO 4. It was found that NiOTiO 2 SO 4 2− containing equimolar composition of NiO and TiO 2 and evacuated at 400 °C for 1.5 hr showed maximum catalytic activity at room temperature. However, NiOTiO 2 which was not treated with H 2SO 4 was inactive as catalyst for ethylene dimerization. Infrared spectra of the H 2SO 4-treated catalyst showed bidentate sulfate ion coordinated to Ti 4+ or Ni 2+. The high catalytic activity of NiOTiO 2 SO 4 2− was correlated with the increase of acid strength by the inductive effect of sulfate ion. The decrease of catalytic activity above 400 °C of evacuation temperature was due to the structural change from amorphous phase to crystalline followed by the decrease of surface area.