Regulation of molecular weight, molecular weight distribution and branching distribution in polyethylene, produced by supported catalysts bearing bis(imino)pyridyl Fe(II) and N,N-α-diimine Ni(II) complexes

For preparation of highly active supported catalyst with bis(imino)pyridyl Fe(II) complexes (Fe۱, Fe۲) and N,N-α-diimine complex of Ni (Ni۳), silica modified with alumina (SiO۲ (Al)) was used as a support. Data on the possibility to regulate molecular weight (MW) and molecular weight distribution (MWD) of polyethylene (PE), produced over the supported catalyst Fe۱/SiO۲ (Al)+TIBA by variation of polymerization temperature and the addition of hydrogen and hexene-۱, are obtained. The prepared PE samples were characterized by Mw values varied from ۸۰ to ۳۵۰ kg/mol and various MMD (Mw/Mn=۴.۶-۱۱.۷).By grafting on SiO۲(Al) of two different iron bis(imino)pyridyl complexes, producing PE with diverse MW, bi-component catalyst was prepared. This catalyst generates linear PE with broad and bimodal MWD (Mw/Mn=۳۳). Fixation on SiO۲(Al) of α-diimine Ni(II) pre-catalyst (Ni۳), yielding high molecular weight branched PE at the ethylene homopolymerization, and bis(imino)pyridyl Fe(II) complex (Fe۲) that forms lower molecular weight linear PE, affords formation of a new bi-component catalyst. The catalyst produces PE with broad MWD and high content of branches concentrated in high molecular weight PE fraction.

Keywords:

Ethylene polymerization , supported catalysts , bis(imino)pyridyl complex of Fe , diimine complex of Ni , molecular weight distribution