| 摘要 |
A catalyst and a process are provided for oligomerizing ethylene. A heterogeneous catalyst system comprises: (1) a chelating ligand, preferably 2-diphenyl phosphino benzoic acid (DPPBA); (2) a nickel precursor, preferably nickel chloride hexahydrate (NiCl2.6H2O); (3) a catalyst activator, preferably sodium tetraphenylborate (NaBPh4); and (4) silica. A 1:1:1 molar ratio of Ni:DPPBA:BPh4 catalyst components are fixed on a silica support using low-temperature fixation. The catalyst components are dispersed in a diluent, preferably ethanol, and silica is added. The ethanol is evaporated using freeze-drying equipment to form a silica-supported catalyst system. The silica-supported catalyst is slurried in ethanol in a reactor, and ethylene is added. The reactor pressure and temperature are maintained at about 725 psig and 100° C., respectively, for about two hours. The oligomer product formed has a narrower weight percent distribution, typically having about 96 weight percent C4's to C10's, compared to product formed using a homogeneous catalyst system.
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