Characterization and evaluation of the nature of chemical species generated in hybrid Ziegler–Natta/metallocene catalyst

Abstract

In the present work CpTiCl 3 pretreated with tri- iso-butylaluminium was immobilized on MgCl 2 supported Ziegler–Natta catalyst. The resulting catalysts were characterized by a series of techniques, namely thermal analysis (TGA/DTA), X-ray photoelectron spectroscopy (XPS), 27 Al magic angle spin nuclear magnetic resonance ( 27 Al MAS–NMR), UV–VIS spectroscopic analysis, inductively-coupled plasma–atomic emission spectroscopy (ICP–AES) and elemental analysis. The catalysts UV–VIS spectrum showed a broad absorption band at 390 nm indicating the presence of metallocene cyclopentadienyl ring. According to XPS analysis, only hybrid catalysts showed two peaks in the Ti (2p 3/2) region after the spectrum deconvolution, a lower binding energy peak at 455 eV and another one at 457 eV (Ti 4+). These appear to be due to difference of electronegativity in the coordination sphere of the Ti due to the TiCl 4 and the Cp( i-Bu)TiCl 2 fixed on the hybrid Ziegler–Natta catalyst. All catalyst systems were active in ethylene-1-butene copolymerization. The resulting polymers obtained with the hybrid catalyst showed a shoulder in the DSC thermogramme fusion peak. It might be caused by a polymer fraction produced by the additional Ti center in the catalyst due to the Cp( i-Bu)TiCl 2. Microscopic analysis showed that the polymer replicated the spherical morphology of the catalyst grain.