New Ways for Controlling the Molecular-Weight Characteristics and Branching Distribution in Polyethylene Obtained over Supported Catalysts Containing Bis(imino)pyridyl Complexes of Fe(II) and Bis(imine) Complexes of Ni(II)

Abstract

The paper describes ways for controlling the molecular structure of polyethylene (PE) produced over supported catalysts containing bis(imino)pyridyl complexes of Fe(II) (LFeCl2) and bis(imine) complexes of Ni(II) (*LFeCl2), which are anchored on silica gel modified by the introduction of alumina (SiO2(Al)). Under variation of polymerization conditions over LFeCl2 /SiO2(Al) catalysts, linear PE with different molecular weight and controllable molecular-weight distribution (MWD) was obtained. Homopolymerization of ethylene over *LNiBr2 /SiO2(Al) catalysts led to the formation of branched PE with the molecular-weight and thermophysical characteristics close to the low-density polyethylene produced by ethylene copolymerization with α-olefins over supported metallocene catalysts and supported Zieglertype catalysts. A method was proposed for constructing the supported bicomponent catalysts containing LFeCl2 and *LNiBr2 complexes anchored on the SiO2(Al) support for the deliberate production of polyethylene with the required molecular structure. There are examples of obtaining the linear PE with bimodal MWD on a bicomponent supported catalyst containing two different LFeCl2 complexes, the PE with controllable branching distribution on a bicomponent catalyst synthesized by anchoring LFeCl2 and *LNiBr2 complexes on the SiO2(Al) support, and an example of modifying the industrial chromium oxide catalyst by introducing the LFeCl2 complex for the control of MWD and branching distribution in the produced polyethylene.