Metallocene catalyst supported on silica–magnesia xerogels for ethylene polymerization

A series of supported metallocene catalysts were prepared by grafting Cp2ZrCl2 on silica–magnesia xerogels, and then they were evaluated for the process of ethylene polymerization. The supports were characterized by a set of complementary techniques including small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N2 adsorption–desorption. The supported catalysts were characterized by Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance infrared spectroscopy (DRIFTS). The use of silica–magnesia xerogels for immobilization of metallocene yielded systems with higher catalyst activity when compared to the results from metallocene grafted on bare silica. The resulting polymers showed a broader molecular weight distribution than those obtained by homogeneous Cp2ZrCl2 and Cp2ZrCl2/SiO2, which potentially provides a better processing capacity of these alternative polyethylenes. In the case of polyethylene obtained with the system containing 16.0 wt.% Mg/Si, a fiber-like morphology was observed.

Graphical abstractA series of supported metallocene catalysts were prepared by grafting of Cp2ZrCl2 on silica–magnesia xerogels and evaluated in ethylene polymerization. The Cp2ZrCl2/SiO2–MgO systems presented higher catalyst activity in comparison to that resulting from the metallocene grafted on bare silica and it allowed the activation using combination of TEA:MAO, employing low Al content.Figure optionsDownload full-size imageDownload high-quality image (52 K)Download as PowerPoint slide