Exploring cocatalyst type effect on the Ziegler–Natta catalyzed ethylene polymerizations: experimental and DFT studies

Masoori, Maryam; Nekoomanesh, Mehdi; Posada‐Pérez, Sergio; Rashedi, Reza; Bahri‐Laleh, Naeimeh

doi:10.1007/s10965-022-03050-1

Cited by 22 publications

(17 citation statements)

References 44 publications

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“…It causes the release of polymer chain. 24 Indeed, to produce film grade with good melt strength, reactor 1 operated at lower temperature and slightly higher H2/C2 ratio while reactor 2 operated at lower H2/C2 ratio and higher comonomer feeding to ensure molecular weight bimodality as well as branching of high molecular weight PE chains. In fact, bimodality of the studied samples was proved by high temperature GPC analysis (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Mansouri

Emami

Yousefi

et al. 2022

J of Applied Polymer Sci

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In this study, the microstructural, flow, and mechanical properties of two commercially available high‐density polyethylene (HDPE) samples with different particle sizes were quantified. Specifically, two different blow molding and film grade HDPEs produced by the same catalyst under different conditions were acquired in powder form after dryer section of an industrial plant. They were fractioned according to their particle sizes into six samples: ≤125, 125–200, 200–315, 315–400, 400–500, and ≥ 500 μm. According to sieve analysis, the film grade (D50 = 304 μm) had larger particle sizes related to the counterpart injection sample (D50 = 289 μm). A peak value in density, bulk density, viscosity molecular weight (Mv), melt flow index (MFI), and comonomer content characteristics was found in the particles with the diameter of 125–200 μm in both samples, indicating extremely non‐homogeneity of these HDPE samples. Chemical composition distribution (CCD) of the as received polymers as well as sieved fractions was surveyed via SSA or TREF analyses. The film sample represented lower MFI and density and higher Mv and comonomer content in all fractions, originated from different reactor conditions during the samples synthesis, which translate into improved mechanical properties comparing with the blow molding sample.

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Section: Resultsmentioning

confidence: 99%

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Mansouri

Emami

Yousefi

et al. 2022

J of Applied Polymer Sci

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“…At the end of this section, it is appropriate to mention the most recent studies by Bahri-Laleh’s group [ 117 , 118 ]. In [ 117 ], ethylene coordination/insertion at different TiEt and TiEt–(μ-Cl) 2 –Al sites ( Figure 10 a–d) was modeled.…”

Section: Complexes Of Timentioning

confidence: 99%

“…In [ 118 ], the catalytic activity of TMCs when using different organoaluminum activators (Et 3 Al, Et 2 AlCl, EtAlCl 2 , and i Bu 3 Al) was studied experimentally, and the effect of Ti–(μ-Cl)–Al bonding on catalytic activity was evaluated theoretically for Ti centers at the (110) MgCl 2 surface and these four organoaluminum compounds. From the results of the modeling, Et 2 AlCl was the best Al component among others.…”

Section: Complexes Of Timentioning

confidence: 99%

Transition Metal–(μ-Cl)–Aluminum Bonding in α-Olefin and Diene Chemistry

2022

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Olefin and diene transformations, catalyzed by organoaluminum-activated metal complexes, are widely used in synthetic organic chemistry and form the basis of major petrochemical processes. However, the role of M–(μ-Cl)–Al bonding, being proven for certain >C=C< functionalization reactions, remains unclear and debated for essentially more important industrial processes such as oligomerization and polymerization of α-olefins and conjugated dienes. Numerous publications indirectly point at the significance of M–(μ-Cl)–Al bonding in Ziegler–Natta and related transformations, but only a few studies contain experimental or at least theoretical evidence of the involvement of M–(μ-Cl)–Al species into catalytic cycles. In the present review, we have compiled data on the formation of M–(μ-Cl)–Al complexes (M = Ti, Zr, V, Cr, Ni), their molecular structure, and reactivity towards olefins and dienes. The possible role of similar complexes in the functionalization, oligomerization and polymerization of α-olefins and dienes is discussed in the present review through the prism of the further development of Ziegler–Natta processes and beyond.

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“…In addition, Bahri-Laleh et al and Posada-Peŕez et al studied the effect of the type and composition of Al-alkyl cocatalysts on ethylene (co)polymerizations. 55,56 High comonomer response in ethylene/α-olefin copolymerizations has been observed in the presence of triisobutylaluminum and diethylaluminum chloride from both experimental and DFT studies.…”

Section: ■ Introductionmentioning

confidence: 97%

New Insights into the Nature of Ti(II) and Ti(III) Active Sites in the Heterogeneous Ziegler–Natta Catalyst

et al. 2023

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This work presents new insights into the nature of the rarely studied Ti(II) active sites in the heterogeneous Ziegler–Natta catalyst. The effect of diethylaluminum chloride (DEAC) on the Ti(II) and Ti(III) active sites as well as their olefin insertion behavior has been systematically investigated by density functional theory (DFT) calculations. The adsorption behavior of AlR n Cl3‑n species (R = Me, Et, and iBu; n = 1,2,3) on the bare Ti(II) active site indicates a more stable bridge mode than the monodentate mode due to the appreciable attraction between the coordinated atom and the Ti center. The monodentate and bridge coordination modes of DEAC on the bare Ti(II) active site significantly influence the geometries of the Ti(II) active sites and the electronic properties of the Ti center. The lower apparent activation energies of propylene insertion than ethylene insertion for the Ti(III) active sites indicate that the Ti(III) active sites are considered to produce copolymers with a high α-olefin content in ethylene/α-olefin copolymerization. The opposite trend in the DEAC-coordinated Ti(II) active sites suggests that they can produce the copolymer with a low α-olefin content in ethylene/α-olefin copolymerization. In addition, the DEAC monodentate-coordinated Ti(II) active site is considered to be the active site for producing oligomers, owing to its lower ΔG AT value (corresponding to termination) than ΔG AI value (corresponding to insertion), which leads to a high tendency of occurrence of termination.

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Exploring cocatalyst type effect on the Ziegler–Natta catalyzed ethylene polymerizations: experimental and DFT studies

Cited by 22 publications

References 44 publications

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Transition Metal–(μ-Cl)–Aluminum Bonding in α-Olefin and Diene Chemistry

New Insights into the Nature of Ti(II) and Ti(III) Active Sites in the Heterogeneous Ziegler–Natta Catalyst

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