Probing into Effects of Support Pre-Treatment on the Polymerization Behavior and Morphology Development of Mg(OEt)2-Based Ziegler–Natta Catalysts

In this study, commercially available, milled, and heat-treated Mg(OEt)2 were used as the precursors in the synthesis procedure of industrially-favorable supported Ziegler–Natta catalysts. The effects of milling and heat-treatment of the support were completely investigated during the catalyst synthesis and polymerization using SEM, PSD, BET, DCS, and XRD techniques. It was found that despite the support treatments had no significant effect on the elemental analysis results of the catalysts, the morphology of the catalyst pores was very sensitive to support manipulation, and bottleneck-type pores were predominated in the catalysts which were made using the non-manipulated supports. On the other hand, the catalysts which were made using the milled and not-milled supports showed a clear difference between the activity, particle size, and particle size distribution of the catalysts. Also, a high level of stacking disorder and high grain size was observed in the crystal structure of the catalyst made using the commercially available support. In the following, competition between fragmentation and replication was investigated in the synthesized samples, and an attempt was made to link the stacking disorder (in the catalyst structure) to the ease of the fragmentation process. Finally, using practical observation, a mechanism was proposed to justify the changes in the morphology of the catalysts during synthesis procedures. We claimed that milling and especially heat-treating of the support leads to the ordering of the MgCl2 stacking structure.