Heterogeneous Ziegler–Natta catalysts with various sizes of MgCl2 crystallites: synthesis and characterization

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• 作者：Eldin Redzic ; Thomas Garoff ; Cezarina Cela Mardare ; Manuela List…
• 关键词：Ziegler–Natta catalyst ; Crystallite size ; Synthesis ; Characterization ; Polyethylene
• 刊名：Iranian Polymer Journal
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：25
• 期：4
• 页码：321-337
• 全文大小：2,025 KB
• 刊物主题：Polymer Sciences; Ceramics, Glass, Composites, Natural Methods;
• 出版者：Springer Berlin Heidelberg
• ISSN：1735-5265

文摘

A MgCl₂-based Ziegler–Natta catalyst was characterized using X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and IR spectra. We focused on the XRD reflection at 2θ = 50° to determine the thickness of MgCl₂ crystals, and validated these results with TEM pictures. SEM pictures were taken in order to measure the size of the nanoparticles formed by the MgCl₂ crystals. Several compounds were synthesized for comparison and to aid interpretation of the infrared (IR) spectra. The catalysts were prepared by precipitating MgCl₂, which was used as support material and subsequently treated with TiCl₄. The thickness of the catalyst crystals was calculated from the XRD reflection at 2θ = 50°. Changing the precipitation temperature within a range from 40 to 90 °C altered the thickness of the MgCl₂ crystal plates. The maximum thickness of 7 nm was achieved at a precipitation temperature of 60 °C. The SEM pictures showed that the nanoparticles had a diameter of ~200 nm. A crystal base unit had a volume that corresponded to that of a sphere of 3.5 nm radius. Thus, we estimated that a typical catalyst particle with a diameter of 20 μm contained about one million nanoparticles, each of which consisted of about 25,000 MgCl₂ crystal units.