Recent advances in polyolefin technology

Propylene Polymerization over MgCl2‐Supported Ziegler–Natta Catalysts Containing Tri‐Ether as the Internal Donor

“…It could be considered as the fifth generation of Ziegler-Natta catalyst. 26 Concerning the high activity and high hydrogen response of the diether-based catalysts, it was reported that dietherbased catalysts had a high content of active sites with low regioselectivity, 19 that this effect can be ascribed to chain transfer after the occasional secondary (2,1-) rather than the usual primary (1,2-) insertion. 27 Additionally, the 1,3-diether strongly coordinates to the support and cannot be easily extracted 2 from the catalyst surface on contact with a cocatalyst such as alkylaluminum 19 because the 1,3-diether show higher affinity toward magnesium chloride than to a cocatalyst, and consequently diether-based catalysts make polypropylene having comparatively high isotacticity without an external donor.…”

“…9 In 1989, the polypropylene catalyst with 1,3-diether as the internal donor was developed by the Himont company. 26 This new internal donor provided a polypropylene catalyst with extremely high activity, isotacticity, hydrogen response, 19 and also narrower MWD without the need for any external donor, 25,26 which breaks the restrictions of the last two generations of catalyst that the polypropylene catalyst, must contain both internal and external donors. It could be considered as the fifth generation of Ziegler-Natta catalyst.…”

“…9 This catalyst is called the fourth-generation Ziegler-Natta catalyst, so far it is still widely used in the polypropylene industry. 26 The requirement for an external donor when using catalysts containing an ester as the internal donor is due to the fact that, when the catalyst is brought into contact with the cocatalyst (most commonly AlEt 3 ), a large proportion of the internal donor is lost as a result of alkylation and/or complexation reactions. In the absence of an external donor, this leads to poor stereoselectivity due to increased mobility of the titanium species on the catalyst surface.…”

“…24 As the electron donors play a major role in the Ziegler-Natta catalyzed propylene polymerization, therefore the development of new electron donors becomes one of the key targets in designing new generation polypropylene catalysts. 3 In the early 1980s, the MgCl 2 -supported catalyst system with a new internal donor, alkyl phthalate, 25,26 and organic siloxane as the external donor was developed. 9 This catalyst is called the fourth-generation Ziegler-Natta catalyst, so far it is still widely used in the polypropylene industry.…”

Stabilized polypropylene synthesis using supported titanium catalyst system in presence of phenolic compounds

“…[1][2][3][4][5] Major improvement in catalyst technology is centered on development of shape-and size-controlled magnesium dichloridesupported titanium catalyst using internal and external donor modifications. [6][7][8][9][10][11][12] These catalyst systems produce polypropylene and its copolymer resin using slurry, bulk, and gas phase polymerization technology with high productivity, controlled stereospecificity, and improved morphological characteristics.…”