Ethylene/1‐Hexene Copolymers Produced with MAO/(nBuCp)₂ZrCl₂ Supported on SBA‐15 Materials with Different Pore Sizes

Abstract

The influence of the support architecture (structure and pore size) on the activity of MAO/(nBuCp)2ZrCl2 heterogeneous catalysts in the polymerization of ethylene and 1‐hexene is studied through the characterization of the polymers' microstructure. SBA‐15 silica‐based mesostructured materials are synthesized with different pore sizes and compared with commercial silica. All SBA‐15 supported catalysts lead to higher catalytic activities than amorphous silica and give rise to ethylene/1‐hexene copolymers with bimodal CCD, which suggests that the carrier structure plays an important role not only in the global rate of the process but also in the copolymer composition. The structures and pore sizes of the support show a marked influence on the polymer CCD shape. magnified image

Influence of Metal‐Alkyls on Early‐Stage Ethylene Polymerization over a Cr/SiO2 Phillips Catalyst: A Bulk Characterization and X‐ray Chemical Imaging Study

“…The DSC results support the STXM results in a sense that indeed we see that the early‐stage PE materials have lower densities than bulk HDPE materials, emphasizing the effect of the support matrix [83, 85] . This is often explained due to PE materials with higher degrees of SCB being less crystalline while still dispersed in the SiO 2 framework and are proposed to be able to diffuse out of the SiO 2 pores, whereas the more crystalline and rigid PE materials are less able to do so [84, 86–88] …”

Silica-supported (n BuCp)2 ZrCl2 : effect of catalyst active center distribution on ethylene-1-hexene copolymerization

“…Now we compare the CCD findings discussed above with those reported for other similar supported metallocenes applied to the copolymerization of ethylene with 1‐hexene. Table shows that the shape of the Crystaf trace (monomodality versus bimodality) depends on several factors such as support and metallocene types, support modification, amount of 1‐hexene fed, etc . We reviewed these published studies and note the following.…”

“…We used silica as the support because of its stability at high temperatures; its availability with varying pore sizes, volumes and surface areas; its low price; and its very large volume usage by industry . We selected ( n BuCp) 2 ZrCl 2 because of its stability, commercial availability at a reasonable price, capability of polymerizing ethylene with high activity in solution and considerable use by researchers in the synthesis of supported metallocene catalysts …”

Synthesis of ultra-high molecular weight poly(ethylene)-co-(1-hexene) copolymers through high-throughput catalyst screening

“…The incorporation of longer chain a-olen monomers into polyethylene chains increases the degree of polymer branching, which lowers the melting point, crystallinity, and density of the polymers. 1 This can lead to signicant increases in polymer exibility, which gives the resultant polymers applications in packaging, foams, elastic bers, and adhesives. 2 Metallocene catalysts containing two h 5 -cyclopentadienyl (C 5 H 5 , Cp) ligands and two s-type ligands (Cp 2 MX 2 ) have similar reactivities with both ethylene and longer chain a-olens; 3 allowing them to incorporate much larger percentages of higher a-olens than traditional Ziegler-Natta catalysts.…”