Influence of THF as Internal‐Donor on Ziegler‐Natta Polyethylene Catalysts

Although Ziegler‐Natta (ZN) catalysts are used since the 1950s, they remain employed in industry because of their robustness and low‐cost relative to many newer catalyst systems. In this study, we investigated the effect of tetrahydrofuran (THF) as an internal donor on the performance of a ZN catalyst for polyethylene (PE) production. Catalysts with varied THF contents were prepared and evaluated under identical polymerization conditions. Catalyst productivity was quantified as (kg poly Ti − 1 h − 1 ), while the resulting polymers were characterized by high‐temperature size‐exclusion chromatography (HT‐SEC), molecular‐weight‐distribution (MWD) deconvolution, and thermal analysis (DSC). Adjusting the amount of internal donor affected catalytic activity. The lowest THF loading increased activity by 27%. Variation of the THF concentration produced changes in productivity, with a maximum at a Ti/THF ratio of 0.5, while higher Ti/THF ratios up to 5, decreased the catalytic activity. The polymer microstructure and properties were insensitive to THF content. HT‐SEC analysis showed miniscule changes in the MWD and the deconvoluted molecular‐weight fractions. Similarly, melting behavior varied only within 1.4°C across the catalyst series. Within experimental uncertainty, THF primarily affects activity rather than polymer characteristics. Thus, tuning the amount of donor provides a practical lever to enhance productivity while preserving the polymer's properties.