Ziegler-Natta catalyst

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A Ziegler-Natta catalyst is a catalyst used in the production of unbranched, stereoregular vinyl polymers. Ziegler-Natta catalysts are typically based on titanium tetrachloride and the organometallic compound triethylaluminium.

These catalysts were discovered in the 1950s by Karl Ziegler, who used a mixture of the above compounds to catalyse the polymerisation of ethylene. Giulio Natta, using the same mixture to catalyse propylene, discovered that the process gave a stereoregular polymer, that is, one with a regular arrangement of side chains.

This stereoregularity is believed to follow from a polymer growth mechanism known as the Cossee-Arlman mechanism, in which the polymer grows at vacant Cl sites at the Ti surface. In the search for a deeper understanding and control of Ziegler-Natta polymerisation at the molecular level, a number of metallocene catalysts have been developed, often offering fine control over the composition and tacticity of the polymer chain so produced. The Kaminsky catalysts are among the products of this effort.