ABSTRACT
Catalysis continues to play a vital role in polymerization of such olefins as ethylene and propylene. Developments toward higher activity Ziegler-Natta catalysts have been based in large part on reactions of specific magnesium, titanium, and aluminum compounds. The efficiency of olefin polymerization catalysts can be improved by several methods. The determination of the concentration of active centers in olefin polymerization systems has received considerable attention. The large changes in polymerization activity using high activity catalysts are mainly due to an increase in the number of active sites. Catalyst characterization studies using a wide range of modern analytical techniques have led to greater insight into the structure and composition of olefin polymerization catalysts. Olefin polymerization is believed to occur via a coordinated anionic mechanism involving a transition metal-carbon bond. Ligand effects in olefin polymerization have provided a better understanding of the steric and electronic factors of importance during the polymerization process.
