Propylene Polymerization over Titanium-Magnesium Catalyst: Effect of Hydrogen on the Content of Active Centers with Different Stereospecificity and Their Reactivity in Propagation Reaction

Abstract

This paper presents data on the number of active centers (CPi) with different stereospecificity and the values of propagation rate constant (kPi) for these centers in the propylene polymerization over supported titanium-magnesium catalyst in the presence or absence of hydrogen. The indicated data were obtained by quenching the polymerization with radioactive carbon monoxide (14CO) with subsequent fractionation of the produced polymers by the TREF method into separate fractions differing in stereospecificity and estimation of the CPi and kPi values, which determine the formation of these fractions. The propagation rate constants calculated for active centers with different stereospecificity increase in the following order: kP(aspecific) ≈ kP(low isospecific) < kP(isospecific) < kP(highly isospecific).