Study On Dimine-nickel Catalyst For Ethylene Polymerization

The polyethylene is the biggest output variety of the world general synthetic resin, holding the pivotal status in the plastics industry. In many polyethylene catalysts, late transition metal olefin polymerization catalysts are new-type catalysts, which have been attracted much attention in recent years. Late transition metal catalysts possess high catalytic activity for olefin polymerization, with single active center and wonderful molecular tailoring properties which could realize molecular design and assembly. They have been becoming the main developing trend of polyethylene industry. Some traits of a series of Nickel-based metal catalysts containingα,α'-diimine ligand using in ethylene polymerization and polymerization conditions on the catalytic properties are studied in this paper. And then, the effect of some alkylaluminum cocatalysts on the catalytic activity is specifically investigated. Five different Nickel-based late transition metal catalysts were synthesized here, accordingly, the ligand structure was confirmed by NMR,elemental analysis and IR method.After that, alkylaluminum cocatalysts were applied in the ethylene atmospheric polymerization system. The results indicated that: the special structure of catalysts had an important influence on the catalytic activity and molecular weight; the best reaction temperature for catalysts a',d' and e' were 0℃, then for catalysts b' and c' were 15℃. With the increase of polymerization temperature, the molecular weight of products were decreased, and theα-olefins proportion of oligomerization products were reduced; ACDA was the best cocatalyst for five different kinds of catalysts; With Al/Ni ratio increasing, activity was increased, but when Al/Ni ratio was greater than certain numerical, the activity of the catalyst began to reduce. in general, when the Al/Ni ratio was about 1000, catalysts show the best activity, catalyst c' can achieve 1.85×10~6g/(molcat·h) when the Al/Ni ratio was 1000.