Preparation of Highly Active Heterogeneous Ziegler-Natta Catalyst for Polymerization of Ethylene

Highly active supported catalyst of Ziegler-Natta type was prepared by reaction of a Grignard reagent. The starting chemicals for preparing MgCl2, the support, were butyl magnesium chloride which mixed with AlCl3 and CH3Si(OC2H5)3, following to two steps treatment of the chemicals with TiCl4 in toluene. Ti Concentration in the solid catalyst was 3.19%. Slurry polymerization of ethylene was carried out using the catalyst in dry heptane, while; triethylaluminium was used as cocatalyst. The cocatalyst effects, such as cocatalyst/catalyst molar ratio, polymerization time, temperature, H2 concentration and the monomer pressure on activity of the catalyst were studied. There was an optimum [Al]/[Ti] molar ratio and temperature to obtain the highest activity of the catalyst. The maximum activity was obtained at 60ºC, and [Al]/[Ti]=714:1. Productivity of 14700 g PE/mmol Ti.h was obtained at monomer pressure of 8 bar. Addition of hydrogen decreased the activity of catalyst and the viscosity average molecular weight (Mv) of the polymer obtained, while; increasing monomer pressure increased its activity. Density of the polymer obtained was 0.93- 0.95 g/cm3 which is in the range of high density polyethylene. Melting point of the polymer was in the range of 140-144ºC.