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<p>The nuclearity of active sites in heterogeneous Ziegler-Natta catalysts fundamentally governs polyolefin microstructure, yet its dynamic regulation during polymerization remains challenging. Here, we report a liquid containing polymerization strategy that directs the formation of dinuclear titanium species through periodic wetting-drying of inert <i>n</i>-hexane on the catalytic particles. Operando spectroscopy reveals how this unique fluid environment promotes the formation of dinuclear centers, in contrast to the monomeric species dominant in conventional gas- or slurry-phase systems. These dinuclear sites substantially enhance comonomer incorporation efficiency, yielding polyethylene with more uniform short-chain branching (SCB) distribution. Diffusion-ordered NMR spectroscopy further confirms that the capillary condensation of inert <i>n</i>-hexane in catalyst pores during liquid containing polymerization can enrich 1‑octene concentration by over twofold compared to the bulk slurry environment, thereby effectively promoting the SCB content in the synthesized polyethylene. This work establishes reactor fluid dynamics as a powerful tool for in-situ active-site engineering, opening avenues for selective control of polymer microstructure without modifying catalyst composition.</p>

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Fluid-mediated nuclearity control in heterogeneous polyolefin catalysis

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年7月2日

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  • Zaitian He,
  • Jingyuan Sun,
  • Qingyuan Zheng,
  • Wei Li,
  • Lynn F. Gladden,
  • Jingdai Wang,
  • Yongrong Yang

摘要

The nuclearity of active sites in heterogeneous Ziegler-Natta catalysts fundamentally governs polyolefin microstructure, yet its dynamic regulation during polymerization remains challenging. Here, we report a liquid containing polymerization strategy that directs the formation of dinuclear titanium species through periodic wetting-drying of inert n-hexane on the catalytic particles. Operando spectroscopy reveals how this unique fluid environment promotes the formation of dinuclear centers, in contrast to the monomeric species dominant in conventional gas- or slurry-phase systems. These dinuclear sites substantially enhance comonomer incorporation efficiency, yielding polyethylene with more uniform short-chain branching (SCB) distribution. Diffusion-ordered NMR spectroscopy further confirms that the capillary condensation of inert n-hexane in catalyst pores during liquid containing polymerization can enrich 1‑octene concentration by over twofold compared to the bulk slurry environment, thereby effectively promoting the SCB content in the synthesized polyethylene. This work establishes reactor fluid dynamics as a powerful tool for in-situ active-site engineering, opening avenues for selective control of polymer microstructure without modifying catalyst composition.