The structure of Ni active sites supported on amorphous silica-alumina supports with different contents of Al₂O₃ loadings in relation to their activities in ethylene oligomerization were investigated. Two kinds of Ni sites were detected by in situ FTIR-CO and H₂-TPR experiments, that are Ni²⁺ cations as grafted on weak acidic silanols and Ni²⁺ cations at ion-exchange positions. The ethylene oligomerization activities of these Ni/ASA catalysts were found an ascending tendency as the Al₂O₃ loading decreased, which could be attributed to the enriched concentration of Ni²⁺ species on acidic silanols with a weaker interaction with the amorphous silica-alumina support. These Ni²⁺ species were more easily to be evolved into Ni⁺ species, which has been identified to be the active sites of ethylene oligomerization. Thus, it seems reasonable to conclude that Ni²⁺ species grafted on acidic silanols were the precursors of active sites.

研究了负载在不同Al ₂ O ₃负载量的无定形二氧化硅-氧化铝载体上的Ni活性位点的结构及其在乙烯低聚中的活性。两种镍网的被检测到的原位FTIR-CO和H ₂ -TPR实验中，为Ni ²⁺阳离子作为弱酸性的硅醇基和Ni接枝²⁺在离子交换位置阳离子。随着Al ₂ O ₃负载量的降低，这些Ni/ASA催化剂的乙烯齐聚活性呈上升趋势，这可能是由于Ni ²⁺的富集浓度。酸性硅烷醇上的物种与无定形二氧化硅 - 氧化铝载体的相互作用较弱。这些Ni ²⁺物种更容易演化为Ni ⁺物种，Ni ⁺物种已被确定为乙烯低聚的活性位点。因此，可以合理地得出结论，接枝在酸性硅烷醇上的Ni ²⁺物种是活性位点的前体。