Synthesis and Characterization of Chromium-Based Catalysts for Ethylene-1-hexene Copolymers Preparation via In- Situ Polymerization of Ethylene

摘要

The tandem catalysis system including the trimerization catalyst of CrCl3/SNS (SNS = bis-(2-pentylsulfanyl-ethyl)-amine) (Cat 1) and the copolymerization catalyst Cat 2 of Cr/SiO2 (Grace 643) has been prepared and used to the synthesis of branched polyethylene. The optimum polymerization conditions were found to be as follows: chromium concentration 0.2 wt %, ethylene pressure 23 bar, solvent hexane, polymerization temperature 90 degrees C, co-catalyst triethylaluminum. The optimally prepared polyethylene was characterized thermally and morphologically. Appearance of alpha and gamma hydrogens in ethylene-1-hexene copolymer confirms the presence of branches in polyethylene backbone.