In-situ and ex-situ microscopic study of gas phase propylene polymerization over a high activity TiCl₄-MgCl₂ heterogeneous Ziegler-Natta catalyst

In-situ gas phase poly(propylene) (PP) formation over a high activity TiCl₄-MgCl₂supported Ziegler-Natta catalyst has been studied by video microscopy combined with ex-situ light microscopy, SEM, high-resolution TEM, and STEM/PEELS/EDX for the first time. In-situ observation revealed rapid formation of poly(propylene) beads 9-10 μm in size (<1/30 s) as well as growth of significant amounts of polymer within local regions. Catalyst particles containing 2-5 nm-sized MgCl₂ crystalline domains are subjected to transformations during catalysis that form PP/catalyst aggregated structures of 30-50 μm in size.