Effect of adduct synthesis parameters on the ethylene polymerization kinetics of Ziegler Natta catalysts

Here, it is aimed to clarify the structure-performance relationship in MgCl2 based Ziegler Natta catalysts toward ethylene polymerizations. In this regard, 11 different adduct precursors were prepared through industrially appreciated melt quenching method employing various: (i) reaction times for dissolving magnesium chloride inside ethanol; (ii) ethanol/MgCl2 molar ratios in the feed; (iii) heating rates during thermal dealcoholation; (iv) N-2 flows during thermal dealcoholation and (v) alcohol content after thermal dealcoholation. Among the studied parameters, heating rate and N-2 flow during thermal dealcoholation have the most pronounced effect on the porosity and particle size of the resulted adducts. Related Ziegler Natta catalysts were subsequently employed in ethylene polymerizations. According to the kinetic curves, catalyst productivity and form of kinetic curve (as decay or build-up type) can be precisely tailored by proper choosing of the mentioned variables during adduct synthesis. Microstructure analysis of the prepared polyethylenes reveals that alcohol content in the final adduct has the most significant effect on the H-2 response, in terms of molar mass and its distribution, of the related Ziegler Natta catalysts. The overall results help polyethylene producers in choosing proper reaction conditions during adduct synthesis for the production of different polymer grades, when productivity or H-2 response is targeted.

Automated summary

In this study, the relationship between the structure and performance of MgCl2 based Ziegler Natta catalysts in ethylene polymerizations was investigated. Different adduct precursors were prepared using the melt quenching method with various reaction conditions. The heating rate and N-2 flow during thermal dealcoholation had the most significant effect on the porosity and particle size of the adducts. The results showed that the alcohol content in the final adduct had a significant impact on the H-2 response and molar mass distribution of the catalysts, providing valuable insights for polyethylene producers in optimizing reaction conditions for different polymer grades.