Pressure‐Decay Kinetic Modeling of Homogeneous Ethylene Polymerization with Et(Ind) ₂ ZrCl ₂ /TIBA‐Borate Catalyst System in a Batch Reactor

ABSTRACT

Solution‐phase ethylene polymerization was conducted in a modified batch reactor equipped with a pressurized injection system for safer transfer of pyrophoric catalyst mixture. Ethylenebis(indenyl)zirconium dichloride [Et(Ind) ₂ ZrCl ₂ ] was used as the metallocene catalyst, activated with triisobutylaluminium (TIBA) and trityl tetrakis(perfluorophenyl)borate (Borate). Polymerization experiments were carried out under varying ethylene pressures and temperatures, and the ethylene consumption was monitored by a decrease in reactor pressure with time. A kinetic model, based on monomer and active‐site balances with first‐order catalyst deactivation, was developed to estimate kinetic parameters directly from pressure–time profiles. The apparent propagation constant k _app increased from about 109.7 s ⁻¹ at 70°C to 156 s ⁻¹ at 90°C, while the deactivation constant k _d rose from ~1.7 × 10 ⁻³  s ⁻¹ to 5.7 × 10 ⁻³  s ⁻¹ , indicating that both propagation and deactivation are accelerated at higher temperatures. Intrinsic propagation rate constants k _p were in the range of 3.0 × 10 ² to 4.6 × 10 ²  L·mol ⁻¹ ·s ⁻¹ , with an activation energy near 22.3 kJ·mol ⁻¹ , whereas catalyst deactivation exhibited a higher activation energy of about 62.7 kJ·mol ⁻¹ . The model also predicted polymer yields in satisfactory agreement with the experimental values. The study establishes pressure decay analysis over time in a batch reactor as a convenient way to quantify propagation and deactivation responses in homogeneous metallocene‐catalyzed ethylene polymerization.