Supported Catalyst (nBuCp)₂ZrCl₂ on Nano/Micro Domains for High Performance Ethylene Polymerization

Abstract

Silica-based supports known as structured-mixed supports were evaluated in ethylene polymerization. These supports exhibit local surface heterogeneity due to the in situ growth of nanoparticles under the surface. Standard (N) and hybrid (NTw and NPu) nanosilicas were synthesized by a sol gel method. The metallocene (nBuCp) 2 ZrCl 2 catalyst was immobilized onto nanosilicas and onto the structured-mixed support (MN, MNTw, and MNPu). The zirconocene active sites on the nanoparticles exhibited high activity (5,071 kg.mol Zr À 1 .h À 1 .bar À 1 with NPu) using Pluronic® L-31 (Pu). An excellent catalytic performance (10,777 kg.mol Zr À 1 .h À 1 .bar À 1 ) was achieved when Zr was incorporated on a structured-mixed support, and a polymer with high molecular weight (Mw up to 224 kg.mol À 1 ), broad polydispersion (Mw. Mn À 1 = 3.1), high melting temperature (Tm = 142 °C), and crystallinity (Xc = 76 %) was generated using Tween®80 (Tw). The results showed that support characteristics, such as a large surface area, surface fractal structure, functionalization of nanoparticles with Tw or Pu, and nano/microdomains, influenced the nature and distribution of active sites, leading to a robust catalytic system that is easily synthesized. Silica-based nano/microparticles pretreated with Tween®80 are an adequate candidate for new catalytic supports for ethylene polymerization.