Optimization of the Preparation Temperature for the Novel (SiO_2/MgO/MgCl_2)⋅TiCl_x Ziegler-Natta Polyethylene Catalyst

摘要

A series of (SiO2/MgO/MgCl2)center dot TiClx Ziegler-Natta polyethylene catalysts have been synthesized using water-soluble Mg-compounds such as magnesium acetate as Mg-source at different TiCl4 treating temperatures. The catalyst shows the highest activity of homopolymerization when preparation temperature is 120 degrees C with only 1.25 of optimal Al/Ti molar ratio, which is much lower than industrial value, resulting in much lower catalyst preparation and polyethylene production cost. The operation condition is relatively moderate and the synthesized catalysts exhibit rather high activity, good hydrogen response, and copolymerization ability with high 1-hexene incorporation. The polymers obtained from these catalysts have high molecular weight and medium molecular weight distribution. Compared with the conventional industrial Ti/Mg Ziegler-Natta catalysts using the relatively expensive, anhydrous and moisture-sensitive Mg-sources, the most unique feature of our novel catalysts is the capability of utilization of any soluble Mg-compounds under mild conditions and can achieve rather high activity with only a small amount of cocatalyst, hence show great potential for application in polyethylene industry.