Research on the controlled synthesis of magnesium ethoxide support for Ziegler-Natta catalysts in olefin polymerization

Abstract

Magnesium ethoxide (Mg(OEt)₂) as a solid precursor for olefin polymerization catalysts was synthesized solely through control of the synthesis process rather than by using external additives. The influence of several important process factors during the preparation of Mg(OEt)₂, such as the addition method of magnesium powder, iodine concentration, ethanol content, and stirring speed, on the properties (particle size, morphology, and bulk density) of Mg(OEt)₂ was investigated. The results show that multi-stage feeding effectively moderates reaction intensity and promotes the ordered assembly and growth of lamellar crystals. This strategy can precisely control the average particle size of Mg(OEt)₂ within the range of 9–34 μm. Under optimized conditions including an I₂/Mg molar ratio of 0.0042, a stirring speed of 200 rpm, and an EtOH/Mg mass ratio of 10.5, we successfully synthesized magnesium ethoxide particles exhibiting a narrow size distribution, high sphericity, a bulk density of 0.37 g/cm³, and excellent flowability. Ziegler-Natta catalysts based on the synthesized Mg(OEt)₂ of varying particle sizes (26.59 and 15.11 micrometers) were evaluated in propylene and ethylene polymerization. The results demonstrate that the size of Mg(OEt)₂ had no significant impact on catalytic activity, it directly determines the particle size distribution of the polyolefin product, thereby influencing its bulk density. This work presents a novel strategy for the industrial synthesis of high-performance, low-cost Ziegler-Natta catalyst supports, providing valuable insights for developing value-added and customized polyolefin products.