TITLE:
Simple Preparation of Halogen-Substituted α-Diimine Nickel Complexes Immobilized into Clay Interlayer as Catalysts for Ethylene Oligo-/Polymerization
AUTHORS:
Miru Yoshida-Hirahara, Shiori Fujiwara, Hideki Kurokawa
KEYWORDS:
Ethylene Oligo-/Polymerization, Heterogeneous Catalyst, Halogen Substituted α-Diimine Nickel Complex, α-Olefin Oligomer, Layered Clay Mineral
JOURNAL NAME:
Modern Research in Catalysis,
Vol.6 No.2,
April
30,
2017
ABSTRACT: In the practical use for the production of the α-olefins, it is highly desired to develop a novel heterogeneous catalyst system. The metal complexes immobilized into the clay interlayers show a great potential as heterogeneous catalysts due to their excellent processability. In this study, nine types of heterogeneous procatalyst Ln/Ni2+-micas were synthesized via a one-pot preparation method, which includes both the condensation reaction of the ligand derivatives and the intercalation of the ligands into the Ni2+ ion-exchanged fluorotetrasilicic mica interlayer. The ligand structures of the prepared procatalysts were [Ln: R-N = C(Nap)-C(Nap) = N-R] [(Nap = 1,8-naphthdiyl) (L1, R = 2-MePh; L2, R = 2-FPh; L3, R = 2-BrPh; L4, R = 4-MePh; L5, R = 4-FPh; L6, R = 4-BrPh; L7, R = 2,4-F2Ph; L8, R = 2,4-Br2Ph; L9, R = 2,6-F2Ph). At 50℃ and 0.7 MPaethylene pressure, the triisobutylaluminum-activated L1-L6/Ni2+-mica showed a catalytic activity for the ethylene oligo-/polymerization in the range of 334 - 549 g-ethylene•g-cat–1•h–1. A high catalyst activity was obtained when the substituent having a larger steric bulk than that of a methyl substituent was introduced at the ortho-position of the aryl rings. The introduction of the fluorine substituent as a strong electron-withdrawing group to the para-position also increased the catalytic activity. The L2, L4, L5, and L6/Ni2+-micas showed moderate selectivities to oligomers consisting of C4-C20 in the range of 19.9 - 41.6 wt% at 50℃. The calculated Schulz-Flory constants α based on the mole fraction of C12 and C14 were within 0.61 - 0.78.