IN SITU SILICA SUPPORTED METALLOCENE CATALYSTS FOR ETHYLENE POLYMERIZATION

Abstract

Bis(2-R-ind)ZrCl2 (R: H or phenyl) was supported on different types of silica by in situ impregnation method and used for ethylene polymerization. In this method, the step of catalyst loading on support was eliminated and common alkyl aluminum (triisobutylaluminum, TiBA) cocatalyst was used instead of expensive methyl aluminiumoxane (MAO) cocatalyst in the polymerization. The effect of surface area of silica on the performance of the supported catalysts using three different types of silica including EP12 (390 m2/gr.), PQ3060 (570 m2/gr.) and MCM-41 (1100 m2/gr.) was investigated. The surface area had a more critical role relative to other characteristics of the support in the performance of catalysts. By using MCM-41 as support, the kinetic stability was enhanced. The activity of the supported catalysts was increased by increasing the surface area of silica in the order of MCM-41 > PQ3060 > EP12. The morphology of polymer particles was improved and reactor fouling was eliminated by supporting the catalyst.

Keywords

• in situ impregnation
• heterogeneous catalysis
• metallocene
• polyethylene
• silica