Peculiarities of ethylene polymerization reactions with heterogeneous Ziegler-Natta catalysts: Kinetic analysis

The previously developed kinetic scheme for olefin polymerization reactions with heterogeneous Ziegler-Natta catalysts states that the catalysts have several types of active centers which have different activities, different stabilities, produce different types of polymer materials, and respond differently to reaction conditions. In the case of ethylene polymerization reactions, each type of center exhibits an unusual chemical feature: a growing polymer chain containing one ethylene unit, Ti-C2H5, is unusually stable and can decompose with the formation of the Ti-H bond. This paper examines quantitative kinetic ramifications of this chemical mechanisms. Modeling of the complex kinetics scheme described in the Scheme demonstrates that it correctly and quantitatively predicts three most significant peculiarities of ethylene polymerization reactions, the high reaction order with respect to the ethylene concentration, reversible poisoning with hydrogen and activation in the presence of a-olefins.