Minoru Terano

The data scientific approach has become an indispensable tool for capturing structure–performance relationships in complex systems, where the quantity and quality of data play a crucial role. In heterogeneous olefin polymerization research, the exhaustive and multi-step nature of Ziegler-Natta catalyst synthesis has long posed a bottleneck in synthetic throughput and data generation. In this contribution, a custom-designed 12-parallel reactor system and a catalyst synthesis protocol were developed to achieve the parallel synthesis of a magnesium ethoxide-based Ziegler-Natta catalyst. The established system, featuring a miniature reaction vessel with magnetically suspended stirring, allows for over a tenfold reduction in synthetic scale while ensuring the consistency and reliability of the synthesis. We demonstrate that the established protocol is highly efficient for the generation of a catalyst library with diverse compositions and physical features, holding promise as a foundation for the data-driven establishment of the structure–performance relationship in heterogeneous olefin polymerization catalysis.

A combination of synchrotron X-ray total scattering and molecular simulation is a powerful approach for reliable determination of the structure of δ-MgCl₂ as an indispensable component of heterogeneous Ziegler–Natta catalysts. Here, the same approach is applied to mechanically activated MgCl₂. Four types of mechanically activated MgCl₂ samples are prepared using ball-milling in the absence and presence of different donors. The development of structural disorder along the grinding time is compared. It was found that the presence of donors accelerates the formation of δ-MgCl₂ in an early stage of grinding, while elongated grinding eventually results in δ-MgCl₂ with similar extents of structural disorder in the absence and presence of different donors. The FT-IR investigation consistently verified the morphological similarity between the firmly ground samples. Thus, the structure of δ-MgCl₂ is likely governed by mechanical energy when sufficiently ground.

The stopped-flow (SF) technique has been extensively applied to study Ziegler–Natta (ZN) olefin polymerization kinetics within an extremely short period (typically <0.2 s) for understanding the nature of the active sites as well as the polymerization mechanisms through microstructure analyses of obtained polymers. In spite of its great applicability, a small amount of polymer that is yielded in a short-time polymerization has been a major bottleneck for polymer characterizations. In order to overcome this limitation, a large-scale SF (LSF) system has been developed, which offers stable and scalable polymerization over an expanded time range from a few tens milliseconds to several seconds. The scalability of the LSF technique has been further improved by introducing a new quenching protocol. With these advantages, the LSF technique has been effectively applied to address several unknown issues in ZN catalysis, such as the role of physical and chemical transformations of a catalyst on the initial polymerization kinetics, and regiochemistry of ZN propylene polymerization. Here, we review the development of the LSF technique and recent efforts for understanding heterogeneous ZN olefin polymerization catalysis with this new system.

The present article reveals important roles of metal alkyl activators in tuning the performance of the Phillips catalyst in ethylene polymerization. The addition of aluminum alkyl aids the activation of the catalyst, while excess addition leads to the loss of the activity. The balance between the activation and deactivation depends on the type of employed aluminum alkyl, and tri‐n‐octylaluminum offers the most efficient catalyst usage by preferentially suppressing the deactivation. The passivation of aluminum trialkyl with a hindered phenol mildens not only the deactivation but also chain transfer reactions, leading to an increment of high molecular weight fractions. image

The origin of the chemical composition of ethylene/propylene copolymer produced with Ziegler–Natta catalysts is investigated in terms of the active site nature and transient monomer concentration during polymerization. Using various catalysts including TiCl₃/MgCl₂ model catalysts with controlled Ti dispersion and TiCl₄/internal donor/MgCl₂ traditional catalysts, normal‐pressure and pressurized slurry copolymerization is conducted at various ethylene/propylene feed ratios. This study finds that the copolymer composition strongly depends on the copolymerization yield rather than the active site nature for both of the normal‐pressure and pressurized copolymerization. The ethylene concentration becomes smaller than its equilibrium concentration during copolymerization primarily due to the great activity enhancement in the copolymerization and secondarily due to the high reactivity and low solubility of ethylene. It is shown that the decrease in the ethylene concentration during copolymerization causes the variation of the copolymer composition in a way dependent on the kinetic profile of employed catalysts, thus broadening the chemical composition distribution. image