Number of Active Centers and Propagation Rate Constants in the Propene Polymerization on Supported Ti-Mg Catalysts in the Presence of Hydrogen
Macromolecular Chemistry and Physics
, E-ISSN: 1521-3935
||ZIEGLER-NATTA CATALYSTS; PROPYLENE POLYMERIZATION; ETHYLENE; POLYPROPYLENE; ACTIVATION; MECHANISM; SYSTEMS
Bukatov Gennadii D.
Goncharov Valerii S.
Zakharov Vladimir A.
Boreskov Institute of Catalysis
Polymerization inhibition with radioactive carbon monoxide was used to determine the number of active centers (Cp) and the propagation rate constant (kp) in the isospecific polymerization of propene with the catalytic system TiCl4/diisobutyl phthalate/MgCl2—AlEt3—PhSi(OEt)3, The presence of hydrogen was found to decrease Cp (by a factor of = 2) and to increase kp (by a factor of = 4). In the absence of hydrogen a considerable part of the active centers (titanium-polymer bonds) reacting with 14CO seems to be inactive in the propene polymerization for steric reasons. Hydrogen is able to transform such centers into an active state. Thus, kp ~ 2,5 • 103 L/'(mol • s) at 70 °C obtained in propene polymerization in the presence of the hydrogen seems to be correct, since the portion of centers in the active state is maximum. The influence of polymerization time, external and internal donors on Cp and kp was studied.