Anchoring via covalent binding of a salicylaldimine-nickel complex in multi-walled carbon nanotubes and its application in ethylene oligomerization

Abstract

Silylated-salicylaldimine nickel(II) (1) was synthesized with 3-aminopropyl-trimethoxysilane, salicylaldimine and NiCl₂·6H₂O, and carbon nanotube-supported salicylaldimine-nickel catalyst (2) was synthesized by anchoring 1 covalently to multi-walled carbon nanotubes. The chemical structure of the synthesized ligand was characterized by elemental analysis, ¹H NMR and FT-IR. Compounds were characterized by XRD, FT-IR, TGA and XPS and were used as precatalysts for ethylene oligomerization. The catalytic activity and the selectivity of C₆ olefin for 2 were much higher than those for 1 in ethylene oligomerization. Compared with other cocatalysts, the catalytic activity and selectivity to C₆ olefin for 2 were the highest using MAO as cocatalyst. When Al/Ni molar ratio was 700, at 25 °C, 30 min and pressure was 0.5 MPa, the catalytic activity of 5.85 × 10⁶ g·(mol Ni·h)⁻¹ and selectivity of 94.7% toward C₆ olefin for 2 in cyclohexane were observed. Compared with 1, catalyst 2 had the good repeatability and thermal stability, with catalytic activity of 4.29 × 10⁶ g·(mol Ni·h)⁻¹ and the selectivity of C₆ olefin was 84.3% after the third oligomerization reaction.

GRAPHICAL ABSTRACT

Keywords:

• Carbon nanotube
• nickel complexes
• covalent modification
• ethylene oligomerization

Acknowledgment

The authors are grateful to State Key Lab of Inorganic Synthesis and Preparative Chemistry of Jilin University for the characterization work.

Disclosure statement

 No conflict of interest exits in the manuscript, and manuscript is approved by all authors for publication.

Additional information

Funding

This work was supported by the Heilongjiang Natural Science Foundation of China (E2018012) for the financial support.