Efficient synthesis of polyethylene wax using 8-(arylimino)-5,6,7-trihydroquinoline SiO2-supported heterogeneous nickel catalysts

In this contribution, a series of nickel complexes based on 8-(arylimino)-5,6,7-trihydroquinoline (Ni1–Ni4) were designed and synthesized. These complexes exhibited high activity of up to 9.0 × 10⁶ g PE/mol Ni·h⁻¹ in ethylene polymerization on treatment with of Et₂AlCl and producing highly branched polyethylene wax (branching numbers range from 66 to 82/1000C). To further improve the performance of these nickel catalysts, the SiO₂-supported catalyst of Ni4 was prepared, which presented better performance compared to homogeneous systems. Especially, the heterogeneous catalysts could further improve activity of up to 16.2 × 10⁶ g PE/mol Ni·h⁻¹, and thermal stability (activity of Ni4–Na@SiO₂ up to 9.0 × 10⁶ g PE/mol Ni·h⁻¹ at 75 °C) through ionic anchoring strategy. The morphology of polyethylene wax obtained by supported catalyst was also controllable. This work may provide an efficient and practical method for preparing polyethylene wax using late-transition metal catalysts.