Catalysts containing various nickel sulfate content were prepared by dry im
pregnation of silica-alumina or silicagel with aqueous solution of nickel s
ulfate. SiO2-Al2O3 alone without NiSO4 was totally inactive for the ethylen
e dimerization reaction at room temperature. However, NiSO4/SiO2-Al2O3 was
found to be very active even at room temperature compared with NiSO4/SiO2.