Gas-phase polymerization of 1,3-butadiene with supported half-sandwich-titanium-complexes

Using half-sandwich-titanium-complexes polybutadiene (BR) can be produced w ith a particular microstructure of about 81% cis, 18% 1,2, and 1% trans uni ts. A stirred bed reactor and a fluidized bed reactor were constructed for gas-phase polymerization of 1,3-butadiene by cyclopentadienyltrichlorotitan ium (CpTiCl3) an MAO (methylaluminoxane) impregnated silica (MAO/SiO2). The major determinant of polymerization activity and molecular weight is the A l-MAO/Ti-ratio on the carrier. Polymerization activity increases to 14 500 kg BR/(mol Ti*h) with a molecular weight of 1.9 x 10(6) g/mol and the catal yst becomes noticeably more stable, Activity further increases when the CpT iCl3 catalyst is prealkylated with small quantities of TIBA (triisobutylalu minium). Systematic methodological experimentation of the heterogenization suggests that a Ti(III)-species is responsible for polymerization. The gas- phase polymerization of 1,3-butadiene reveals a rate of polymerization whic h is considerably greater than the equivalent rate in the homogeneous syste m. The polymers all have similar characteristics, pointing to the same acti ve species. The microstructure of the polybutadiene produced was investigat ed by spectroscopic measurements and by hydration; a preference to block st ructures of 1,2-units could not be established.