Supported Ziegler–Natta catalyst for ethylene polymerization: Novel data on the effect of polymerization temperature on the number of active centers and propagation rate constant

• The number of active centers changes with ethylene polymerization temperature.
• This changing is more significant than the propagation rate constant changing.
• Temperature coefficient of variation of the number of active centers was calculated.
• The activation energy of the chain propagation reaction was obtained.

The number of active centers at ethylene polymerization over highly active supported catalyst TiCl4/MgCl2 + AlEt3 was determined at various polymerization temperatures. It was found that the increase in polymerization temperature in the range of 40–80 °C increases the number of active centers. The data on reversible changes in the polymerization rate with temperature in a single experiment give grounds for supposing that alteration of the number of active centers with temperature is a reversible process. The propagation rate constants and the activation energy of the propagation reaction (4.0 kcal mol− 1) were calculated; the latter value being considerably lower than the effective activation energy of polymerization (16.5 kcal mol− 1) due to the increase in CP with rising temperature.

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