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Dataset of energetically accessible structures of MgCl₂/TiCl₄ clusters for Ziegler-Natta catalysts.

ABSTRACT: This data article provides a dataset of the energetically accessible structures including the most stable structures of xMgCl₂/yTiCl₄ nanoplates (x?=?6-19, y?=?0-4). TiCl₄-capped MgCl₂ nanoplates are regarded as the building block of the Ziegler-Natta catalyst. The most stable structures were determined for MgCl₂/TiCl₄ nanoplates of different sizes and chemical compositions using a combination of the genetic algorithm and the DFT geometry optimization. The evolution in the genetic algorithm produced a number of meta-stable structures. A set of isomeric structures having similar energy to the most stable structure (termed energetically accessible structures) are provided as realistic models of MgCl₂/TiCl₄ nanoplates. These structures are useful for further investigation on the structural distribution of Ti species on MgCl₂ regarding the Ziegler-Natta catalyst.

SUBMITTER: Takasao G

PROVIDER: S-EPMC7753921 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Dataset of energetically accessible structures of MgCl2/TiCl4 clusters for Ziegler-Natta catalysts.

Takasao Gentoku G Wada Toru T Thakur Ashutosh A Chammingkwan Patchanee P Terano Minoru M Taniike Toshiaki T

Data in brief 20201215

This data article provides a dataset of the energetically accessible structures including the most stable structures of xMgCl2/yTiCl4 nanoplates (x = 6-19, y = 0-4). TiCl4-capped MgCl2 nanoplates are regarded as the building block of the Ziegler-Natta catalyst. The most stable structures were determined for MgCl2/TiCl4 nanoplates of different sizes and chemical compositions using a combination of the ge ...[more]

PMID: 33364274

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Project description: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-? 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.

Dataset Information

Dataset of energetically accessible structures of MgCl₂/TiCl₄ clusters for Ziegler-Natta catalysts.

Publications

Dataset of energetically accessible structures of MgCl<sub>2</sub>/TiCl<sub>4</sub> clusters for Ziegler-Natta catalysts.

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