Oligomerization of Ethylene to Produce Linear α-Olefins Using Heterogeneous Catalyst Prepared by Immobilization of α-Diiminenickel(II) Complex into Fluorotetrasilicic Mica Interlayer
Heterogeneous catalysts for production of linear α-olefins from ethylene were prepared by the direct reaction of the α-diimine ligand [ L: R-N=C(R')-C(R')=N-R; R' = Me and R = 2,6-Me 2Ph ( L5), 2,5-Me 2Ph ( L1), 2-MePh ( L2), or Ph ( L3); R' = 1,8-naphth-diyl and R = Ph ( L 4)] and Ni 2+ ion-exchanged fluorotetrasilicic mica. Only high molecular weight polyethylene was obtained in the reaction using the L5/Ni 2+-Mica procatalyst activated by AlEt 3 (TEA) as an activator, whereas the TEA-activated L1- and L2/Ni 2+-Mica procatalysts afforded a mixture of a large amount of low-molecular weight polyethylene and a small amount of oligomers having 4-22 carbons. The procatalyst consisting of Ni 2+-Mica and the L3 ligand that possesses non-substituted phenyl groups on the iminonitrogen atoms effectively promoted the oligomerization of ethylene after its activation with TEA, resulting in the fact that the ethylene oligomers were produced with a moderate catalytic activity (101 g-ethylene g-cat ？1 h ？1 at 0.7 MPa-ethylene) in the presence of TEA. When the backbone was varied from the butane moiety ( L3) to acenaphthene ( L4), the solid product dramatically increased. The weight percentage of the oligomers in the total products increased with the increasing reaction temperature; however, an insignificant increase in the oligomers was observed when the ethylene pressure was decreased.
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