| Magnesium Chloride supported catalyst with proper external Lewis-base has high activity and high stereospecificity for olefin polymerization. The supported CW-catalyst MgCl(,2)/Ethylbenzoate/p-cresol/AlEt(,3)/TiCl(,4) with cocatalyst AlEt(,3)(.)Methyl-p-toluate has been thoroughly characterized. Chemical composition of supports and catalyst have been determined by elemental analysis and gas chromatography. Double redox titrations showed the distribution of Ti oxidation states in catalyst were 50% of Ti('+4), 40% of Ti('+3) and 10% of Ti('+2). Only one fifth of the Ti('+3) was observable by EPR. The addition of coactivators reduced Ti to lower oxidation states: 10% of Ti('+4), 70% of Ti('+3) and 20% of Ti('+2). The physical states of the materials obtained during each stages of catalyst preparation were studied by BET, porosimetry and x-ray diffraction techniques. Final catalyst has surface area ca. 110 - 150 m('2) g('-1). The ultimate crystallite size 20 A - 30 A of MgCl(,2) was obtained by ball-milling with ethyl benzoate for 60 h.;The kinetic of propylene polymerization was studied using same catalyst. The active sites concentration were determined by radio-tagging with tritiated methanol and ('14)CO. The results are in agreement with those obtained by kinetic methods. There are at least four different kinds of active center exist in catalyst. By varying polymerization conditions such as Cat , C(,3)H(,6) , temperature and Al to Ti ratio, the propagation rate constant K(,p), activating energy of propagation, (DELTA)E(,p), the termination constant, K(,t), were determined. The average molecular weight and molecular weight distribution have been examined by GPC, viscometry, and end group analysis. The rate constant of chain transfer with monomer, K(,tr,M), and rate constant of (beta)-hydride transfer, K(beta), were calculated. The effect of hydrogen on propylene polymerization has been studied. The rate of polymerization was increased with H(,2) that is caused by the increasing of active centers.;By comparing the profiles of polymerization of propylene to insoluble PP and of decene-1 to soluble PD with the same catalyst. We concluded that the polymerization rate decay is not caused by monomer diffusion limitations. |
