Industrially Developed Ziegler-Natta Catalysts

Current Industrially Developed Ziegler-Natta Catalysts 

In current industrial practice, coordinated anionic catalysts differ considerably from the original ones, developments by Ziegler, Natta, and others. Using the same basic chemistry, new compounds were developed over the years that yield large quantities of polyolefins from small amounts of catalysts. In addition, catalysts can now be designed to yield products that are either wide or narrow in molecular weight distribution, as needed. The new catalysts for ethylene polymerization can be divided into three groups  

Products from reactions of trivalent alkoxy chlorides of transition metals with certain halogen-fi-ee organoaluminum compounds, e.g., triisobutylaluminum. Such catalysts are used without any support. 

Products from reactions of magnesium compounds with titanium compounds. In these catalysts the transition metals are attached chemically to the surfaces of solid magnesium com- 

Titanium compounds bonded to the surface OH groups of Mg(OH)2 are mainly inactive. The active sites are the ones associated with the coordinated and unsaturated negative oxygen ions. Reactions with aluminum alkyls activate the catalysts. For high efficiency, special carriers must be used together with a correct balance of the reactants, and proper reaction conditions. Some choice combinations of reactants are  

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Current Industrially Developed Ziegler-Natta Catalysts... 

Since the discovery of Ziegler-Natta catalysts, polyolefin industries have been developed mainly by using titanium-based catalysts. However, after the appearance of metallocene catalysts, much emphasis has been placed on those based on zirconium owing to the superiority of their performance over titano-cene catalysts. 

What are the advantages of half-sandwich metallocene-based catalysts as compared with heterogeneous Ziegler-Natta catalysts in styrene polymerisation What are the possible consequences of this for developing industrial processes ... 

However, no method of polymerisation known before 1954 allowed one to obtain polymers with a high regularity of structure from the most common conjugated dienes. A true breakthrough in the development of conjugated diene rubbers took place after the discovery of stereospecific polymerisation with transition metal-based coordination catalysts. From the late 1950s, a rapid development of industrial production of solution types of polybutadiene by means of polymerisation with Ziegler-Natta catalysts was observed. 

The discovery of active magnesium chloride as the ideal support for the fixation of titanium tetrachloride and its derivatives opened a new era in the field of Ziegler-Natta catalysis, both from the industrial and the scientific viewpoint. During the last 15 years MgCl2-supported catalysts brought about revolutionary industrial developments, as compared to those of the traditional Ziegler-Natta catalysts. 

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