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RESEARCH PRODUCT

The roles for a Lewis base and MgCl2 in third-generation Ziegler-Natta catalysts

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Activity of a titanium catalyst supported on a bimetallic magnesium-aluminium system, involving a Lewis base [MgCl2(THF) 2 /Al(C 2 H 5 ) 2 Cl], was studied in ethylene polymerization, and the effect of the catalyst composition on the properties of the final polymer produced was investigated. Analysis and discussion of the findings covering also some part of the kinetic study, resulted in defining the roles for MgCl 2 and a Lewis base in the third-generation Ziegler-Natta catalysts. MgCl 2 forms a bimetallic complex with an organoaluminium compound, which involves also a Lewis base. Its reaction with TiCl 4 yields a very active catalyst wherein the Mg: Ti molar ratio is close to 1. This means that MgCl 2 is involved in creating catalytic active sites. The structure of these catalytic sites were suggested. Hence, the role for MgCl 2 can be twofold: it is a component of a catalytic active site, and it is a support if Mg: Ti > 5. It was found in the study that the catalytic function of MgCl 2 can be maintained while its supporting function can be omitted. Thus, MgCl 2 can be substituted for Al 2 O 3 and the catalytic system obtained will have the same activity.