Chemical dealcoholation of MgCl2EtOH adduct by Al compounds and its effect on the performance of Ziegler-Natta catalysts

MgCl2nEtOH adducts play a major role in the industrial production of polyethylenes. Their chemical dealcoholation, usually accomplished during the catalyst synthesis step, has had a pronounced impact on the microstructure of the final Ziegler-Natta pre-catalysts and the properties of the resulting polymers. Due to the industrial and academic importance of this issue, different aluminum-based compounds including triethylaluminum (TEAL), triisobutylaluminum (TIBA), and ethylaluminumdichloride (EADC) were used in this research in the chemical dealcoholation of a MgCl21.5EtOH adduct, to provide the target catalysts. According to the analytical results, the catalysts synthesized using aluminum compounds (especially TEAL and EADC) generally had a more fractured structure, a smaller particle size and a vast surface area. Aluminum precursors bind to the catalyst structure together with TiCl4, which is manifested from their higher adsorption energies obtained by DFT calculations, and the presence of Al atom in the elemental analysis. Varying the chemical structure and physical properties of the catalysts, established using Al compounds, caused significant variation in the ethylene polymerization kinetic curves, their related rate constants, and the flow characteristic of the final polymers. The overall results outstandingly affirm that by appropriate choice of the Lewis acid compound, during the chemical dealcoholation of the adduct, various Ziegler-Natta catalysts can be achieved for different polyethylene grades.

Automated summary

The chemical dealcoholation of MgCl2nEtOH adducts has a significant impact on the industrial production of polyethylenes. This study investigates the use of aluminum-based compounds in the dealcoholation process and their effects on the microstructure of catalysts and properties of polymers. The results show that the choice of Lewis acid compound during dealcoholation can lead to different Ziegler-Natta catalysts for different polyethylene grades, affecting the polymerization kinetics and flow characteristic of the final polymers.