Commercial Methods for the Synthesis of Ziegler-Natta Catalysts for the Production of Polyethylene: A Patent Review

F or more than sixty years, thousands of patents and articles have been published annually on various manufacturing methods of Ziegler-Natta catalysts and comparing the properties and performance of the obtained catalysts. However, a closer look at these documents reveals that the basic and commercial methods of manufacturing these catalysts may be very limited and that other methods are either not commercializable or are merely subsets of these original methods. In this paper, by reviewing the wide range of numerous patents patented over the past four decades, the main production methods of commercial Ziegler-Natta magnesium-titanium catalysts are categorized based on the morphology of the obtained catalyst. The morphology of Ziegler-Natta catalysts can be divided into two categories: spherical morphology and non-spherical morphology. The morphology of Ziegler-Natta catalysts is one of the most important variables that determines the possibility of using a special catalyst in the polymerization process (gas phase or suspension). Catalysts with spherical morphology can be produced by commercial methods of emulsion, impregnation, and spray drying. In contrast, catalysts with non-spherical morphology can also be produced by commercial methods of reactive precipitation and support conversion