Effects of diethyl aluminum chloride (DEAC) addition to the catalysts prepared by reduction of TiCl4 with EtMgCl on ethylene-propylene copolymerization

Abstract

TiCl3/2.5MgCl2(0.5MgEt2)/THF catalyst (R) was prepared by the reduction of TiCl4 with EtMgCl. The effect of diethyl aluminum chloride (DEAC) addition on the catalytic activity in ethylene-propylene copolymerization was investigated. It was suggested from FT-i.r. that the catalyst R formed similar bimetallic (Ti-Mg-THF) complexes to the TiCl3(AA)/3MgCl2/THF catalyst (T3ME) of our previous report [7]. An ESR study provided evidence that the Ti3+ species in the catalyst R was of the multinuclear type, instead of an isolated type of T3ME, and it changed from a tetrahedral to an octahedral structure with addition of DEAC. The activities of R catalysts in copolymerization were more or less in the same order of magnitude with each other due to the multinuclear nature of the Ti3+ species, and the response to propylene comonomer decreased with addition of DEAC. The polydispersity of comonomer over R catalysts was in the range of 6-10, being much broader than that over the T3ME catalyst system. It might be due to the heterogeneity of the titanium(III) structure; tetrahedral as well as octahedral in R, instead of only octahedral in T3ME.