The effects of partial replacement of TiCl₄ by Ti(OR)₄ on the performance of MgCl₂-supported Ziegler-Natta catalysts

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• 作者：Cristó ; vã ; o de Lemos^a ; Fernando Franceschini^a ; Claudio Radtke^b ; Joã ; o H.Z. dos Santos^b ; ^{jhzds@iq.ufrgs.br} ; Carlos R. Wolf^c
• 关键词：Ziegler&ndash ; Natta catalyst ; High-density polyethylene ; Titanium tetra-alkoxide
• 刊名：Applied Catalysis A ; General
• 出版年：2012
• 期刊代码：4_0926860x
• 类别：ch
• 出版时间：7 May, 2012
• 卷：423-424
• 期：Complete
• 页码：69-77
• 文件大小：796 K

摘要

In a Ti-based Ziegler-Natta catalyst with in situ generated MgCl₂, the titanium tetrachloride (TiCl₄) was partially replaced by titanium tetra-alkoxide (Ti(OR₄)), where R was either ethyl or n-butyl, and the effect of the addition order of the titanium compound was evaluated. For comparison, two other catalysts were synthesized: (1) one had the same amount of Ti, exclusively from TiCl₄; (2) the other is employed in industrial processes and was used as the reference. Ti³⁺ comprised 85%of the total amount of titanium added during the catalyst synthesis. The amount of soluble Ti in the supernatant phase was at most 0.002 mol L^鈭?, indicating that the added Ti reacted with the support. In general, Ziegler-Natta catalysts demand a significant amount of raw materials, while these catalysts require a lower amount of titanium compounds and save a significant amount of solvent in particular during the synthesis (approximately 80%). The preparation time of the catalysts was also reduced. The performance of these catalysts during ethylene polymerization suggests that adding Ti(OR)₄ created a catalyst with a similar activity and ability to form high-density polyethylene as the reference catalyst.