Diffusion controlled stereoregular polymerization in granule reactors- Reaction kinetic of Pr/Bt sequence polymerization with TiCl4/MgCl2 Ziegler-Natta catalyst

Diffusion controlled stereoregular polymerization was studied to understand the relations between fragmenta-tion and growing of catalyst granules and its catalytic features for olefin polymerizations. In this work, propylene (Pr) polymerization kinetics and Pr/butene-1 (Bt) sequence polymerization kinetics with spherical TiCl4/MgCl2 Ziegler-Natta catalyst were investigated by monitoring catalytic activity (CA), the number of active centers ([C*]/[Ti]) and microstructure of polymers. It was found that the increase in Pr polymerization time benefiting to the catalyst granule fragmentation, had different influences on the [C*]/[Ti] and catalytic efficiency (CE) for Bt-stage polymerization in different stage. Anyway, the isotacticity and weight-average molecular weight (Mw) of isotactic polybutene-1 (iPB) fractions decreased gradually with the increase in Pr polymerization time. It was deduced that the easy solubility of polybutene-1 (PB) brought difficulties in further fragmentation of catalyst particles to expose more active centers, and Bt was more sensitive to the chemical and steric environment around the active species. This work provides further understanding of the catalytic characteristics of granule reactors in the initial polymerization stage, which will guide the novel polyolefin alloy production.

Automated summary

Diffusion controlled stereoregular polymerization was studied to investigate the relations between catalyst granules fragmentation and growing and its catalytic features. Propylene (Pr) polymerization kinetics and Pr/butene-1 (Bt) sequence polymerization kinetics with spherical TiCl4/MgCl2 Ziegler-Natta catalyst were investigated. The results showed that the increase in Pr polymerization time had different influences on the [C*]/[Ti] and catalytic efficiency (CE) for Bt-stage polymerization in different stage, and the isotacticity and weight-average molecular weight (Mw) of iPB fractions decreased gradually with the increase in Pr polymerization time.