The Nature of the Active Site in Ziegler–Natta Olefin Polymerization Catalysis Systems – A Computational Investigation

Kumawat, Jugal; Gupta, Virendra K.; Vanka, Kumar

doi:10.1002/ejic.201402180

Cited by 31 publications

(40 citation statements)

References 83 publications

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“…Nevertheless,h aving ac atalysts ystem having as maller or nonexistent induction period would be preferable to having ac atalyst system with al ong induction period, if their subsequenta ctivities are comparable, which is the case for most donor-included Z-N systems, as seen from previous calculations. [52] In addition, in the Z-N reaction, ab arrierh eight of 37.9 kcal mol À1 is not formidable. Thisi sb ecause the temperature employed in Z-N catalysis systemsisu sually greater than 60 8C.…”

Section: Comparative Study Between Wd(ticl 4 )And the Donorsmentioning

confidence: 99%

Effect of Donors on the Activation Mechanism in Ziegler–Natta Catalysis: A Computational Study

2016

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Full quantum chemical calculations, using density functional theory (DFT), have been conducted to explain the effect of donors on the “activation mechanism” in the Ziegler–Natta (Z–N) catalyst system. In the activation mechanism, the inactive TiIVCl4 catalyst converts into the active TiIIICl2Et catalyst with the help of the AlEt3 present in the system. The donors that have been considered in this study are: ethyl benzoate (eb), two representative diether cases, a phthalate donor, and a silyl ester donor. The results indicate that eb and the diether donor cases donor have a negative effect on the barriers for the activation mechanism. However, the eb donor can be displaced from the MgCl2 surface by AlEt3, which matches experimental observations. For the phthalate, silyl ester and TiCl3–OC4H8Cl cases, the results indicate that a significant induction period would be present in Z–N systems employing such donors or having such a catalytic center, before catalysis could commence.

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Section: Comparative Study Between Wd(ticl 4 )And the Donorsmentioning

confidence: 99%

Effect of Donors on the Activation Mechanism in Ziegler–Natta Catalysis: A Computational Study

2016

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“… 5 , 7 , 14 , 17 , 18 Some computational studies go one step further and look at the role that the donors play in the whole catalytic cycle. 19 − 21 …”

Section: Introductionmentioning

confidence: 99%

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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“…Ziegler‐Natta (ZN) catalysis is one of the most important catalytic processes, which produces around 150 million tons of polyolefins/year, and has a billion dollar market [1] . Since its discovery in the 1950s by Karl Ziegler and Giulio Natta, for which they received the Nobel prize in 1963, [2,3] continuous efforts to improve the performance of the ZN systems, concerning their activity and the selectivity, have been undertaken, along with understanding at the molecular level, by employing various experimental [4–11] and computational tools [12–34] . The main components of the ZN system are (i) MgCl 2 as a catalyst support, (ii) TiCl 4 as precatalyst, (iii) triethylaluminum ( teal ) as an alkylating agent, and (iv) Lewis base donors (e. g. oxygen‐containing molecules and nitrogen‐containing polymers [35] ).…”

Section: Introductionmentioning

confidence: 99%

“…Donors are vital components of the ZN polymerization process that can enhance the stereo‐ and regioselectivity of the product by coordinating in the vicinity of the active titanium center [9,42,43,46] . It can influence the kinetics of the activation, insertion and termination steps in the polymerization reaction, and can also help the titanium to coordinate to the (104) MgCl 2 surface, which is otherwise unutilized [30,31,33] . It is interesting to note that tuning the structure of existing donors and developing new donors has always been challenging and a prominent area of research in ZN catalysis, because of their potential to produce polyolefins with desirable properties.…”

Section: Introductionmentioning

confidence: 99%

Insights into the Nature of Self‐Extinguishing External Donors for Ziegler‐Natta Catalysis: A Combined Experimental and DFT Study

et al. 2020

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Developing donors for Ziegler‐Natta (ZN) catalysis to control the polymerization reaction and produce polymers with desirable properties has always been challenging due to the multi‐component nature of the catalytic systems. Here, we have developed a new synthetic protocol for making two external donors, D1 (2,2,2‐trifluoroethyl myristate) and D2 (2,2,2‐trifluoroethyl palmitate) that show self‐extinguishing properties, followed by a systematic DFT study to understand this peculiar property of these donors. D1 and D2 can undergo parallel reactions with aluminum and titanium species present in the system to produce ketones and aldehydes, which are poisons for ZN catalytic systems, thus explaining their self‐extinguishing nature. The non‐covalent interaction between the long alkyl chain of the donors with the surface plays a vital role in determining the donors′ self‐extinguishing nature. There is a significant thermodynamic preference for the binding of the donor with the longer alkyl chain at the titanium center. The current work, therefore, provides interesting insights into how self‐extinguishing donors function in ZN catalytic systems.

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The Nature of the Active Site in Ziegler–Natta Olefin Polymerization Catalysis Systems – A Computational Investigation

Cited by 31 publications

References 83 publications

Effect of Donors on the Activation Mechanism in Ziegler–Natta Catalysis: A Computational Study

Effect of Donors on the Activation Mechanism in Ziegler–Natta Catalysis: A Computational Study

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

Insights into the Nature of Self‐Extinguishing External Donors for Ziegler‐Natta Catalysis: A Combined Experimental and DFT Study

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The Nature of the Active Site in Ziegler–Natta Olefin Polymerization Catalysis Systems – A Computational Investigation

Cited by 31 publications

References 83 publications

Effect of Donors on the Activation Mechanism in Ziegler–Natta Catalysis: A Computational Study

Effect of Donors on the Activation Mechanism in Ziegler–Natta Catalysis: A Computational Study

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

Insights into the Nature of Self‐Extinguishing External Donors for Ziegler‐Natta Catalysis: A Combined Experimental and DFT Study

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