Polypropylene growth on silica‐supported metallocene catalysts: A microscopic study to explain kinetic behavior especially in early polymerization stages

Abstract

The polypropylene growth on metallocene/MAO catalysts supported on a silica carrier has been examined by scanning electron microscopy. The kinetic induction period in early polymerization stages can be explained by the formation of a discrete polymer layer only on the outer surface of the catalyst particle. Differences in the fragmentation process at later stages are pointed out, depending on the supporting procedure of the catalyst system. Acta Polymer., 48,392-399 0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim 1997

Development of a refined poly(propylene) growth model for silica supported metallocene catalyst systems

“…Fig. 1 shows the bulk structure of the catalyst system 2 in comparison with the industrial system 1 2) , that comprises a noticeable cavity structure arising from an additional spray drying process. Because of the much more uniform structure in comparison with the industrial system 1, the supporting material for system 2 is more suitable for investigating the polymer growth.…”

Unusual ethylene polymerization results with metallocene catalysts supported on silica

“…In contrast, the catalyst prepared by the suspension method showed a penetration of catalyst components throughout the entire particle. 14,17 Ethylene polymerization was conducted at 20°C and 2 bars ethylene pressure with catalyst 1. After certain periods of time the reaction was stopped in order to analyse the polymer particles formed.…”

Silica supported metallocene/MAO-systems: comparison of the polypropylene growth during bulk phase polymerization with slurry phase experiments

“…During our investigations of the propylene bulk polymerization with a silica supported metallocene/MAO catalyst system, it was possible to transfer the polymer growth model arising from experiments in toluene slurry phase 1,2) to technically relevant conditions. Despite the considerably higher monomer concentration when polymerizing in propylene bulk phase, we were able to point out strong diffusion limitations during the reaction.…”

“…Microtome section of a polymerized catalyst particle resulting from 7 min propylene polymerization with catalyst system 1 in liquid propylene at 30 8C concentration in comparison with slurry polymerizations in an organic solvent. The goal of this paper is to show possibilities for comparing the polymer growth in liquid propylene with the polymer growth already investigated in slurry phase 1,2) . Even at the markedly more drastic conditions when polymerizing in bulk phase, it is possible to delay the start of the reaction by lowering the reaction temperature to investigate early polymerization stages.…”

“…Lowering the reaction temperature enables the investigation of the polymer growth in early reaction stages and leads to the development of a particle growth model for silica supported metallocene/MAO catalyst systems 1,2) . Heterogeneous industrial polymerization catalysts are primarily developed for the drop-in application into existing gas phase or bulk phase production plants.…”