Solid-state NMR studies of Ziegler–Natta and metallocene catalysts

Tijssen, Koen C.H.; Blaakmeer, E.S.; Kentgens, A.P.M.

doi:10.1016/j.ssnmr.2015.04.002

Cited by 15 publications

(13 citation statements)

References 102 publications

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“…Solid-state NMR can be a valuable tool to study the active constructs in heterogeneous catalysis as well as to study the interactions between different catalyst components. − In particular, when NMR is combined with density functional theory (DFT) calculations, this can yield in-depth information, also for ZNC model systems. , Here, we also apply the solid-state NMR/DFT approach to study binary adducts of MgCl 2 support and organic electron donors to obtain experimental proof for surface constructs that are formed. 1 H and 13 C solid-state NMR are used for the study of the IDs, and the interpretation of the NMR results is supported by DFT calculations of the 13 C chemical shift tensor.…”

Section: Introductionmentioning

confidence: 99%

Structural Characterization of Electron Donors in Ziegler–Natta Catalysts

et al. 2018

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Ziegler–Natta catalysis is a very important industrial process for the production of polyolefins. However, the catalysts are not well-understood at the molecular level. Yet, atomic-scale structural information is of pivotal importance for rational catalyst development. We applied a solid-state NMR/density functional theory tandem approach to gain detailed insight into the interactions between the catalysts’ support, MgCl2, and organic electron donors. Because of the heterogeneity of the samples, large line widths are observed in the carbon spectra. Despite this, good agreement between experimental and computational values was reached, and this shows that 1,3-diether based donors coordinate at (110) surface sites, while phthalates are less selective and coordinate at both (104) and (110) surface sites.

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Section: Introductionmentioning

confidence: 99%

Structural Characterization of Electron Donors in Ziegler–Natta Catalysts

et al. 2018

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“… 30 It is our belief that the final answers about the working mechanisms of ZNCs will primarily be found when studying the catalysts themselves. 31 …”

Section: Introductionmentioning

confidence: 99%

“…30 It is our belief that the final answers about the working mechanisms of ZNCs will primarily be found when studying the catalysts themselves. 31 This calls for a wide range of experimental studies making use of the strengths of different spectroscopic techniques, including solid-state NMR spectroscopy. A few recent studies 32−34 have shown the potential of a combined 1 H and 13 C solid-state NMR/density functional theory (DFT) approach for the study of the organic donors on the catalysts' surface, giving valuable experimental proof for standing hypothesis about preferred coordination modes.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Recent years have seen more experimental studies that focus on structure–function relationships, for both traditional MgCl 2 -based ZNCs − and new MgCl 2 -derived support materials. − Still, many studies try to investigate the produced polymer in intricate ways to learn more about these elusive catalysts via an indirect approach . It is our belief that the final answers about the working mechanisms of ZNCs will primarily be found when studying the catalysts themselves …”

Section: Introductionmentioning

confidence: 99%

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Probing Interactions between Electron Donors and the Support in MgCl₂-Supported Ziegler–Natta Catalysts

Blaakmeer

Antinucci

Eck³

et al. 2018

J. Phys. Chem. C

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Olefin polymerization using Ziegler–Natta catalysts (ZNCs) is an important industrial process. Despite this, fundamental insight into the inner working mechanisms of these catalysts remains scarce. Here, we focus on the low-γ nuclei 25Mg and 35Cl for an in-depth solid-state NMR and density functional theory (DFT) study of the catalyst’s MgCl2 support in binary adducts prepared by ball-milling. Besides the bare MgCl2 support and a MgCl2–TiCl4 adduct, samples containing donors that are part of the families of 2,2-dialkyl-1,3-dimethoxypropanes and phthalates used in fourth- and fifth-generation ZNCs are studied. DFT calculations indicate that the quadrupolar coupling parameters of the chlorines differ significantly between bulk and surface sites. As a result, the NMR visibility of the chlorine sites correlates with the particle size except for the adduct with 2,2-dimethyl-1,3-dimethoxypropane donor. The DFT calculations furthermore show that the surface sites are fairly insensitive to binding of different donor molecules, making it difficult to identify specific binding motives. The surface sites with large 35Cl NMR line widths can be observed using high radio frequency field strengths. For the 2,2-dimethyl-1,3-dimethoxypropane donor, we observe additional surface sites with intermediately high quadrupolar couplings, suggesting a different surface structure for this particular adduct compared to the other systems. For 25Mg, pronounced effects of donor binding on the quadrupole interaction parameters are observed, both computationally and experimentally. Again the adduct with the 2,2-dimethyl-1,3-dimethoxypropane donor shows a different behavior of the surface sites compared to the other adducts, which display more asymmetric coordinations of the surface Mg sites. Identifying specific binding motives by comparing 25Mg NMR results to DFT calculations also proves to be difficult, however. This is attributed to the existence of many defect structures caused by the ball-milling process. The existence of such defect structures both at the surface and in the interior of the MgCl2 particles is corroborated by NMR relaxation studies. Finally, we performed heteronuclear correlation experiments, which reveal interactions between the support and Mg–OH surface groups, but do not provide indications for donor–surface interactions.

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“…For this purpose, several experimental [29][30][31][32][33][34][35] and computational 13,15,[36][37][38][39][40][41][42][43][44][45][46] studies were performed. Many features of the catalyst, as the structure of the precatalyst, the activation process, the oxidation state(s) of the active titanium species during the polymerization process were investigated; notwithstanding, there are still several open questions.…”

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confidence: 99%

Structural Characterization of the EtOH–TiCl₄–MgCl₂ Ziegler–Natta Precatalyst

et al. 2016

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The Ziegler-Natta polymerization is one major example of application of catalysis in industry. Since the first discovery of the Ziegler and Natta, several modifications of the catalyst have been developed, in order to improve its performances. Nowadays, a typical Ziegler-Natta catalyst for polyethylene synthesis consists of a precatalyst, composed by TiCl 4 supported on MgCl 2 in presence of a Lewis base, activated by organoaluminium.The atomic-scale characterization of the Ziegler-Natta catalyst is crucial for further improvement of the catalyst. Here, the precatalyst TiCl 4 -MgCl 2 with EtOH as internal Lewis base is characterized combining solid-state NMR spectroscopy and periodic density functional theory calculations. From total energy and NMR spectra, 8 surface species were proposed showing EtO -ligands on the Ti and EtOH/EtO -on the surface Mg species. These species lead to a complete interpretation of the NMR 2D spectra.Hence a detailed molecular scale description of the pre-catalyst was obtained.

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Solid-state NMR studies of Ziegler–Natta and metallocene catalysts

Cited by 15 publications

References 102 publications

Structural Characterization of Electron Donors in Ziegler–Natta Catalysts

Structural Characterization of Electron Donors in Ziegler–Natta Catalysts

Probing Interactions between Electron Donors and the Support in MgCl₂-Supported Ziegler–Natta Catalysts

Structural Characterization of the EtOH–TiCl₄–MgCl₂ Ziegler–Natta Precatalyst

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Solid-state NMR studies of Ziegler–Natta and metallocene catalysts

Cited by 15 publications

References 102 publications

Structural Characterization of Electron Donors in Ziegler–Natta Catalysts

Structural Characterization of Electron Donors in Ziegler–Natta Catalysts

Probing Interactions between Electron Donors and the Support in MgCl2-Supported Ziegler–Natta Catalysts

Structural Characterization of the EtOH–TiCl4–MgCl2 Ziegler–Natta Precatalyst

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Probing Interactions between Electron Donors and the Support in MgCl₂-Supported Ziegler–Natta Catalysts

Structural Characterization of the EtOH–TiCl₄–MgCl₂ Ziegler–Natta Precatalyst