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

In a Ti-based Ziegler-Natta catalyst with in situ generated MgCl2, the titanium tetrachloride (TlCl4) 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-1, 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. (C) 2012 Elsevier B.V. All rights reserved.