Active centers in Ziegler-Natta catalysts: Formation kinetics and structure

► Kinetics of ethylene polymerization with Ziegler-Natta catalysts is studied. ► Temperature, 1-alkenes, H2 and IITi species affect the rate of active center formation. ► Amount of cocatalyst and ethylene concentration do not affect active center formation. ► Rates of active center formation for different IVTi and IIITi-based catalysts are similar. ► Active centers are formed in IVTi (IIITi) → IITi-(ethylene) → IVTi reaction sequence.