Hydrogen and comonomer effects on Ziegler-Natta catalyzed propylene polymerization using different types of alkoxysilane external donor

摘要

Alkoxysilanes are the most commercially used external donor in propylene polymerization using Ziegler-Natta (ZN) catalyst. It is known that the molecular structure of alkoxysilane such as the number and size of alkoxy groups as well as the size of alkyl groups attached to the silicon atom affects the catalyst performance[l]. However the systematic establishment of structure-performance relationship (SPR) for various types of alkoxysilane has not been satisfactory acquired, especially under different polymerization conditions. In our previous work, the relationship between polymerization performances in stopped-flow (SF) and slurry polymerization and alkoxysilane structures was compared with the calculated active site performances based on coadsorption model. It was found that an alkoxysilane adsorbed strongly on MgCl2 surfaces tended to give a higher polymer yield and the conformation detail of alkyl structures around active sites was essential for stereospecificity improvement[2]. In the present study, the effects of alkoxysilane structures on the comonomer incorporation and the hydrogen response in propylene polymerization were investigated, aiming at the SPR information of alkoxysilane structures for the further development of new donor system.