Effect of AlEt3 and an External Donor on the Distribution of Active Sites According to Their Stereospecificity in Propylene Polymerization over TiCl4/MgCl2 Catalysts with Different Titanium Content. Issue 12 (4th May 2016) - Nikolaeva, Marina
Abstract : The data on content of individual fractions with different microtacticity for poly(propylene) (PP) samples produced over titanium–magnesium catalysts (TMCs) with composition TiCl4 /MgCl2 and different titanium contents (0.1 and 3.5 wt%), as well as on the effects of pretreatment of these catalysts with triethylaluminum and addition of an external electron donor to the polymerization reaction on the content of these fractions are obtained using preparative temperature rising elution fractionation. The TMC with low titanium content is found to contain more than 90% of aspecific sites and an insignificant number of sites with low isospecificity (IS1 ) and isospecific sites (IS2 ). Pretreatment of catalysts with triethylaluminum increases the contents of the IS1 and IS2 sites. Addition of an external donor results in a more noticeable increase in the contents of IS1 and IS2 sites and formation of highly isospecific IS3 sites. The data on molecular weight and thermophysical properties of individual PP fractions with different microtacticity produced over catalysts with different compositions are obtained. Abstract : New data on the formation of active sites with different stereospecificity at propylene polymerization over TiCl4 /MgCl2 catalysts with low titanium content (0.1 wt%) and their transformations after pretreatment of catalyst with AlEt3 and addition of external donor have been found. The data are obtained by analysis of results of poly(propylene) fractionation by preparative temperature rising elution fractionation.