Polymerization of Ethylene over Highly Active Catalysts Containing Mono- and Di-ester Lewis Base;Determination of Active Site Concentration

Abstract

The concentration of active sites (C*) for the polymerization of propylene has been compared with that for the polymerization of ethylene using highly active Mg(OEt)2/benzoyl chloride(PhCOCl)/TiCl4 catalysts (containing monoester) or MgCl2/butanol/phthaloyl chloride [Ph(COCl)2]/TiCl4 catalyst (containing diester) activated with AlEt3. The method used to measure a concentration of active sites is based on the inhibiting effect of carbon monoxide on polymerization. Depending on the strength of interaction between catalytic species and internal Lewis base anchored onto catalyst matrix, there was much difference between the C*-values for propylene polymerization and those for ethylene polymerization. While the C*-values for propylene polymerization measured at the maximum polymerization rate (Rp.m) were in the range between 0.17 and 0.33 mol/mol Ti, the C*-values for ethylene polymerization were in the range between 0.28 and 0.45 mol/mol Ti. In order to investigate the stability of active sites during polymerization the C* values have been compared at various polymerization times of determination. The C*-values were constant or increased for ethylene polymerizations, which was completely different trend for propylene polymerizations.