Effect of Free Trimethylaluminum Content in Methylaluminoxane on Performances of Bis(salicylaldiminate)nickel(II)‐Based Catalysts for Ethylene Polymerization

Abstract

Summary: The performances of ethylene polymerization catalysts based on III and commercial methylaluminoxane were investigated by reducing the content of free trimethylaluminum in methylaluminoxane by its reaction with 2,6‐di‐tert‐butylphenol. This allowed optimization of the formulation of the catalyst, affording a high‐molecular‐weight linear polyethylene (PE) with a productivity [(1 900 kg of PE/(mol of Ni × h)], ten‐fold higher than that previously achieved for the same system adopting commercial methylaluminoxane not pre‐treated with the above phenol derivative. magnified image

Titanium (IV) and Nickel (II) Catalysts Based on Anilinotropone Ligands

“…Similar to other natural nickel ethylene polymerization catalysts which have already been reported for oligomerization of -olefins [64,65], oligomerization of 1-hexene at 40 and 60 °C by catalyst 14 led to low yields of oligomers with degrees of polymerization of 21 and 16, respectively [62]. Branching numbers are 147 and 152 branches per 1000 carbon atoms, indicating a very minor amount of chain straightening via a 2,1-insertion and chain walking [39].…”

Zirconocene Propylene Polymerisation: Controlling Termination Reactions

“…The chemical treatment can be carried out by sterically hindered phenols such as 2,6-di-tert-butyl-4-methylphenol (BHT), which is reported to react with TMA. [13,14] The use of TMA-free MAO for catalyst activation has been recently reported by Busico et al [15] and Carlini et al [16] In the absence of an external chain transfer agent, chain termination in propylene polymerisation with a zirconocene/MAO catalyst system can occur via b-H/b-CH 3 transfer to Zr, b-H transfer to monomer and chain transfer to aluminium. [2,17] To determine the operative termination reactions in olefin polymerisation, it is necessary to analyse M w dependency on the polymerisation conditions, in particular on the monomer pressure.…”

Vinyl polymerization of norbornene by bis(nitro‐substituted‐salicylaldiminate)nickel(II)/methylaluminoxane catalysts

“…NB was employed as a 20 wt % solution in the solvent adopted for the polymerization. XIII , XV , and XVI were prepared as previously described 19, 20, 23, 24…”

“…Therefore, this article deals with the homopolymerization of NB by cheap, stable, and very easily synthesized bis(salicylaldiminate)Ni(II) complexes in the presence of MAO, which have been claimed by us to be very active in ethylene activation 19, 20. Indeed, bis(salicylaldiminate)Ni(II) complexes {bis[ N ‐(2,6‐diisopropylphenyl)salicylaldiminate]nickel(II) ( XIII ) and XIV ; Chart } were reported to be recently employed in NB polymerization 21, 22 .…”