Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Ethylene Polymerization via Zirconocene Catalysts and Organoboron Activators: An Experimental and Kinetic Modeling Study

Version 1 : Received: 25 November 2020 / Approved: 26 November 2020 / Online: 26 November 2020 (09:44:35 CET)

A peer-reviewed article of this Preprint also exists.

Valencia, L.; Enríquez-Medrano, F.; López-González, R.; Quiñonez-Ángulo, P.; Saldívar-Guerra, E.; Díaz-Elizondo, J.; Zapata-González, I.; León, R.D. Ethylene Polymerization via Zirconocene Catalysts and Organoboron Activators: An Experimental and Kinetic Modeling Study. Processes 2021, 9, 162. Valencia, L.; Enríquez-Medrano, F.; López-González, R.; Quiñonez-Ángulo, P.; Saldívar-Guerra, E.; Díaz-Elizondo, J.; Zapata-González, I.; León, R.D. Ethylene Polymerization via Zirconocene Catalysts and Organoboron Activators: An Experimental and Kinetic Modeling Study. Processes 2021, 9, 162.

Journal reference: Processes 2021, 9, 162
DOI: 10.3390/pr9010162

Abstract

After 40 years of the discovery of metallocene catalysts, there are still several aspects that remain unresolved, especially when the “conventional” alkylaluminum activators are not used. Herein, we systematically investigate the synthesis of PE via three different zirconocene catalysts, with different alkyl substituents, activated via different organoboron compounds. The polymerization behavior, as well as the properties of the materials, are evaluated. The results demonstrate that the highest catalytic activity is shown by Bis(cyclopentadienyl)dimethylzirconium activated by trityl tetra(pentafluorophenyl)borate. Also finding that toluene is the optimum solvent for these systems and at these reaction conditions. Moreover, to validate our experimental results, a comprehensive mathematical model is developed on the basis of thermodynamic and kinetic principles. The concentration of ethylene transferred to the solvent phase (toluene) in a liquid-vapor equilibrium (LVE) system is estimated based on the Duhem’s theorem. Arrhenius expressions for the kinetic rate constants of a proposed kinetic mechanism are estimated by a kinetic model, in which the rate of polymerization is fitted by a least-square optimization procedure and the molecular weight averages by the method of moments. The simulations of the coordination polymerization suggest the presence of two types of active sites, principally at low temperatures, and the reactivation of the deactivated sites via a boron-based activator. However, the effect of the temperature on the reactivation step is no clear; a deeper understanding via designed experiments is required.

Subject Areas

Ethylene polymerization; metallocene; zirconium-based catalyst; organoboron compounds; kinetic modeling.

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