Abstract
AbstractThe effect of external Lewis base (Be) on the polymerization of ethylene by the MgCl2/ethyl benzoate/p‐cresol/AlEt3/TiCl4 catalyst was studied by activation with AlEt3 alone without the use of methyl‐p‐toluate. The initially formed active site concentration, [Ti], is about doubled in the absence of Be; at 50°C about 93% of the total titanium became catalytic. The same increment of [Ti] was observed without Be. The rate constants of propagation are not appreciably affected by Be; the values are the same at 50° with and without Be. At other temperatures the kp values are somewhat smaller without Be. One major effect was the very large k values for chain transfer with aluminum alkyls in the absence of Be as compared to those with Be. This can be attributed to the greater monomeric AlEt3 concentration in the former, but in much smaller amounts in the presence of Be due to complexation. The rate constants of chain transfer with hydrogen are not much affected by Be. However, the termination rate constants are generally much smaller when Lewis base is not present.
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