Dataset Information

Disclosing the Interaction between Carbon Monoxide and Alkylated Ti³⁺ Species: a Direct Insight into Ziegler-Natta Catalysis.

ABSTRACT: In the field of Ziegler-Natta catalysis for olefin polymerization, carbon monoxide (CO) is used in the industrial practice to quench the reaction when it proceeds too fast, approaching critical levels for the plant safety. The quenching effect is explained as due to the reversible coordination of CO to the titanium active sites, but no direct evidence has been ever reported. In this work, we designed a series of experiments to monitor CO adsorption at variable temperatures on a model Ziegler-Natta catalyst by means of FT-IR spectroscopy. For the first time, we have been able to spectroscopically detect CO coordinated to alkylated Ti³⁺ sites and the Ti-acyl species formed upon the subsequent insertion of CO into the Ti³⁺-alkyl bond, both in the absence and in the presence of the olefin monomer. In perspective, this has important implications for the characterization of the active sites in industrial Ziegler-Natta catalysts, even under working conditions.

SUBMITTER: Piovano A

PROVIDER: S-EPMC8008442 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Disclosing the Interaction between Carbon Monoxide and Alkylated Ti<sup>3+</sup> Species: a Direct Insight into Ziegler-Natta Catalysis.

Piovano Alessandro A Zarupski Jelena J Groppo Elena E

The journal of physical chemistry letters 20200701 14

In the field of Ziegler-Natta catalysis for olefin polymerization, carbon monoxide (CO) is used in the industrial practice to quench the reaction when it proceeds too fast, approaching critical levels for the plant safety. The quenching effect is explained as due to the reversible coordination of CO to the titanium active sites, but no direct evidence has been ever reported. In this work, we designed a series of experiments to monitor CO adsorption at variable temperatures on a model Ziegler-Nat ...[more]

PMID: 32584046

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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-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.

Dataset Information

Disclosing the Interaction between Carbon Monoxide and Alkylated Ti³⁺ Species: a Direct Insight into Ziegler-Natta Catalysis.

Publications

Disclosing the Interaction between Carbon Monoxide and Alkylated Ti<sup>3+</sup> Species: a Direct Insight into Ziegler-Natta Catalysis.

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Disclosing the Interaction between Carbon Monoxide and Alkylated Ti3+ Species: a Direct Insight into Ziegler-Natta Catalysis.

Publications

Disclosing the Interaction between Carbon Monoxide and Alkylated Ti<sup>3+</sup> Species: a Direct Insight into Ziegler-Natta Catalysis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

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Disclosing the Interaction between Carbon Monoxide and Alkylated Ti³⁺ Species: a Direct Insight into Ziegler-Natta Catalysis.