Exploring the role of ester electron donors in ethylene polymerization using bi-supported SiO2@MgCl2/TiCl4 type Ziegler-Natta catalysts

Abstract This study aimed to explore the effects of ester-based internal electron donors on the efficacy and characteristics of SiO₂@MgCl₂ bi-supported Ziegler-Natta (ZN) catalysts. Four distinct ester-based electron donors were used during catalyst synthesis, including linear diesters with varying carbon chain lengths (diethyl succinate and diethyl malonate), aromatic diesters (di-n-butyl phthalate), and aromatic monoesters (ethyl benzoate). Synthesized catalysts were employed in ethylene polymerizations using H₂ as molar mass moderator. Various analytical techniques and measurements of bulk density were employed to analyze the prepared catalysts and polymers. SEM analysis revealed that most catalyst particles had a spherical morphology, except for the catalyst incorporating malonate as internal electron donor. The phthalate catalyst showed a larger diameter, mainly due to its role as a binding agent. The molecular weight, activity, and bulk density of polyethylene were found to be influenced by the type of electron donors. The catalyst with SiO₂@MgCl₂/THF/TiCl₄/ethyl benzoate exhibited significantly higher catalytic activity and hydrogen response, which can be attributed to the reduced steric hindrance surrounding the ethyl benzoate compound. These findings have implications for the development of more efficient and sustainable polymerization processes, with potential applications in various industries using polyethylene.