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63 pages, 19681 KB

Open AccessReview

MAO- and Borate-Free Activating Supports for Group 4 Metallocene and Post-Metallocene Catalysts of α-Olefin Polymerization and Oligomerization

by Ilya E. Nifant’ev, Pavel D. Komarov, Oksana D. Kostomarova, Nikolay A. Kolosov and Pavel V. Ivchenko

Polymers 2023, 15(14), 3095; https://doi.org/10.3390/polym15143095 - 19 Jul 2023

Cited by 8 | Viewed by 5205

Abstract

Modern industry of advanced polyolefins extensively uses Group 4 metallocene and post-metallocene catalysts. High-throughput polyolefin technologies demand the use of heterogeneous catalysts with a given particle size and morphology, high thermal stability, and controlled productivity. Conventional Group 4 metal single-site heterogeneous catalysts require [...] Read more.

Modern industry of advanced polyolefins extensively uses Group 4 metallocene and post-metallocene catalysts. High-throughput polyolefin technologies demand the use of heterogeneous catalysts with a given particle size and morphology, high thermal stability, and controlled productivity. Conventional Group 4 metal single-site heterogeneous catalysts require the use of high-cost methylalumoxane (MAO) or perfluoroaryl borate activators. However, a number of inorganic phases, containing highly acidic Lewis and Brønsted sites, are able to activate Group 4 metal pre-catalysts using low-cost and affordable alkylaluminums. In the present review, we gathered comprehensive information on MAO- and borate-free activating supports of different types and discussed the surface nature and chemistry of these phases, examples of their use in the polymerization of ethylene and α-olefins, and prospects of the further development for applications in the polyolefin industry. Full article

(This article belongs to the Special Issue Catalytic Applications in Polymerization)

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11 pages, 2029 KB

Open AccessArticle

Polymerization of Allyltrimethylisilane and 4-Methyl-1-Pentene by Using Metallocene Catalysts

by Wei Wang, Minqiao Ren, Liping Hou, Shuzhang Qu, Xinwei Li and Zifang Guo

Polymers 2023, 15(9), 2038; https://doi.org/10.3390/polym15092038 - 25 Apr 2023

Cited by 3 | Viewed by 2546

Abstract

Polymers of higher olefin, obtained by Ziegler-type polymerization, have been used in some critical fields, e.g., as the membrane for extracorporeal membrane oxygenation (ECMO), which plays an important role in the treatment of patients with severe COVID-19. The polymer obtained by a single-site [...] Read more.

Polymers of higher olefin, obtained by Ziegler-type polymerization, have been used in some critical fields, e.g., as the membrane for extracorporeal membrane oxygenation (ECMO), which plays an important role in the treatment of patients with severe COVID-19. The polymer obtained by a single-site catalyst, e.g., metallocene catalysts, demonstrated a higher performance. The homo- and co-polymerization of allyltrimethylisilane (ATMS) and 4-methyl-1-pentene (4M1P) were conducted using syndiospecific (cat 1) and isospecific (cat 2) metallocene catalysts. Cat 1 showed low conversions and provided a polymer with a higher molecular weight, while cat 2 behaved oppositely. ¹³C-NMR spectra certified the stereotacticity of the resultant polymer, and the resonance of the carbon atom of CH₂ (αα’) between the two tertiary carbon atoms of the ATMS and 4M1P units were observed. This could be the evidence of the formation of a true copolymer. The crystallization of the polymer was explored using a differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD). All homopolymers and some of the copolymers showed high melting temperatures and low melting enthalpies. The WAXD patterns of the syndiotactic polymer and isotactic homopolymer or the ATMS-rich copolymer were consistent with the reported literature, but the isotactic 4M1P-rich copolymer provided the crystal form I, which is unusual for a 4M1P polymer without any pretreatment. Full article

(This article belongs to the Special Issue Innovative and Functionalized Polymers: Processing, Development and Applications)

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62 pages, 20590 KB

Open AccessReview

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

by Ilya E. Nifant’ev, Ildar I. Salakhov and Pavel V. Ivchenko

Molecules 2022, 27(21), 7164; https://doi.org/10.3390/molecules27217164 - 23 Oct 2022

Cited by 5 | Viewed by 4356

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Frontiers in Metal Complexes)

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25 pages, 4270 KB

Open AccessArticle

Investigations on the Ethylene Polymerization with Bisarylimine Pyridine Iron (BIP) Catalysts

by Elsa M. Schoeneberger and Gerrit A. Luinstra

Catalysts 2021, 11(3), 407; https://doi.org/10.3390/catal11030407 - 23 Mar 2021

Cited by 7 | Viewed by 5220

Abstract

The kinetics and terminations of ethylene polymerization, mediated by five bisarylimine pyridine (BIP) iron dichloride precatalysts, and activated by large amounts of methyl aluminoxane (MAO) was studied. Narrow distributed paraffins from initially formed aluminum polymeryls and broader distributed 1-polyolefins and (bimodal) mixtures, thereof, [...] Read more.

The kinetics and terminations of ethylene polymerization, mediated by five bisarylimine pyridine (BIP) iron dichloride precatalysts, and activated by large amounts of methyl aluminoxane (MAO) was studied. Narrow distributed paraffins from initially formed aluminum polymeryls and broader distributed 1-polyolefins and (bimodal) mixtures, thereof, were obtained after acidic workup. The main pathway of olefin formation is beta-hydrogen transfer to ethylene. The rate of polymerization in the initial phase is inversely proportional to the co-catalyst concentration for all pre-catalysts; a first-order dependence was found on ethylene and catalyst concentrations. The inhibition by aluminum alkyls is released to some extent in a second phase, which arises after the original methyl groups are transformed into n-alkyl entities and the aluminum polymeryls partly precipitate in the toluene medium. The catalysis is interpretable in a mechanism, wherein, the relative rate of chain shuttling, beta-hydrogen transfer and insertion of ethylene are determining the outcome. Beta-hydrogen transfer enables catalyst mobility, which leads to a (degenerate) chain growth of already precipitated aluminum alkyls. Stronger Lewis acidic centers of the single site catalysts, and those with smaller ligands, are more prone to yield 1-olefins and to undergo a faster reversible alkyl exchange between aluminum and iron. Full article

(This article belongs to the Special Issue Homogeneous Catalysis with Earth-Abundant Metal Complexes)

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13 pages, 5246 KB

Open AccessArticle

Zirconocene-Catalyzed Dimerization of α-Olefins: DFT Modeling of the Zr-Al Binuclear Reaction Mechanism

by Ilya Nifant’ev, Alexander Vinogradov, Alexey Vinogradov, Stanislav Karchevsky and Pavel Ivchenko

Molecules 2019, 24(19), 3565; https://doi.org/10.3390/molecules24193565 - 2 Oct 2019

Cited by 19 | Viewed by 4126

Abstract

Zirconocene-mediated selective dimerization of α-olefins usually occurs when precatalyst (η⁵-C₅H₅)₂ZrCl₂ is activated by minimal excess of methylalumoxane (MAO). In this paper, we present the results of density functional theory (DFT) simulation of the initiation, [...] Read more.

Zirconocene-mediated selective dimerization of α-olefins usually occurs when precatalyst (η⁵-C₅H₅)₂ZrCl₂ is activated by minimal excess of methylalumoxane (MAO). In this paper, we present the results of density functional theory (DFT) simulation of the initiation, propagation, and termination stages of dimerization and oligomerization of propylene within the framework of Zr-Al binuclear mechanism at M-06x/DGDZVP level of theory. The results of the analysis of the reaction profiles allow to explain experimental facts such as oligomerization of α-olefins at high MAO/(η⁵-C₅H₅)₂ZrCl₂ ratios and increase of the selectivity of dimerization in the presence of R₂AlCl. The results of DFT simulations confirm the crucial role of the presence of chloride in the selectivity of dimerization. The molecular hydrogen was found in silico and proven experimentally as an effective agent that increases the rate and selectivity of dimerization. Full article

(This article belongs to the Special Issue Recent Advances in DFT: Theory, Simulations and Applications)

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40 pages, 1686 KB

Open AccessReview

The Influence of Ziegler-Natta and Metallocene Catalysts on Polyolefin Structure, Properties, and Processing Ability

by Ahmad Shamiri, Mohammed H. Chakrabarti, Shah Jahan, Mohd Azlan Hussain, Walter Kaminsky, Purushothaman V. Aravind and Wageeh A. Yehye

Materials 2014, 7(7), 5069-5108; https://doi.org/10.3390/ma7075069 - 9 Jul 2014

Cited by 161 | Viewed by 33455

Abstract

50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced [...] Read more.

50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced polymers. New metallocene/methylaluminoxane (MAO) catalysts open the possibility to synthesize polymers with highly defined microstructure, tacticity, and steroregularity, as well as long-chain branched, or blocky copolymers with excellent properties. This improvement in polymerization is possible due to the single active sites available on the metallocene catalysts in contrast to their traditional counterparts. Moreover, these catalysts, half titanocenes/MAO, zirconocenes, and other single site catalysts can control various important parameters, such as co-monomer distribution, molecular weight, molecular weight distribution, molecular architecture, stereo-specificity, degree of linearity, and branching of the polymer. However, in most cases research in this area has reduced academia as olefin polymerization has seen significant advancements in the industries. Therefore, this paper aims to further motivate interest in polyolefin research in academia by highlighting promising and open areas for the future. Full article

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19 pages, 1016 KB

Open AccessArticle

Metallocene Based Polyolefin Nanocomposites

by Walter Kaminsky

Materials 2014, 7(3), 1995-2013; https://doi.org/10.3390/ma7031995 - 10 Mar 2014

Cited by 24 | Viewed by 8679

Abstract

One of the most efficient and versatile ways to synthesize polyolefin nanocomposites is the in-situ polymerization of olefins in the presence of nano particles by metallocene catalysts. Metallocene/methylaluminoxane (MAO) catalysts are soluble in hydrocarbons and therefore they can be absorbed perfectly in solution [...] Read more.

One of the most efficient and versatile ways to synthesize polyolefin nanocomposites is the in-situ polymerization of olefins in the presence of nano particles by metallocene catalysts. Metallocene/methylaluminoxane (MAO) catalysts are soluble in hydrocarbons and therefore they can be absorbed perfectly in solution onto the surface of particles or fibers and after addition of ethene or propene they can then catalyze a polyolefin film on the surface. Metallocene/MAO and other single site catalysts allow the synthesis of polymers with a precisely defined microstructure, tacticity, and stereoregularity as well as new copolymers with superior properties such as film clarity, high tensile strength and lower content of extractables. The polymer properties can be enlarged by the incorporation of nanofillers. The resulting polyethylene or polypropylene nanocomposites give a tremendous boost to the physical and chemical properties such as dramatically improved stiffness, high gas barrier properties, significant flame retardancy, and high crystallization rates. Full article

(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)

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11 pages, 573 KB

Open AccessArticle

Precise Active Site Analysis for TiCl₃/MgCl₂ Ziegler-Natta Model Catalyst Based on Fractionation and Statistical Methods

by Shougo Takahashi, Toru Wada, Toshiaki Taniike and Minoru Terano

Catalysts 2013, 3(1), 137-147; https://doi.org/10.3390/catal3010137 - 7 Feb 2013

Cited by 18 | Viewed by 7525

Abstract

In heterogeneous Ziegler-Natta catalysts for olefin polymerization, isolation of a single type of active sites is a kind of ambition, which would solve long-standing questions on the relationship between active site and polymer structures. In this paper, polypropylene produced by TiCl₃/MgCl [...] Read more.

In heterogeneous Ziegler-Natta catalysts for olefin polymerization, isolation of a single type of active sites is a kind of ambition, which would solve long-standing questions on the relationship between active site and polymer structures. In this paper, polypropylene produced by TiCl₃/MgCl₂ model catalysts with minimum Ti heterogeneity was analyzed by combined solvent fractionation and the two-site statistical model. We found that the active sites of the model catalysts were classified into only three types, whose proportions were dependent on the Ti dispersion state. The addition of external donors not only newly formed highly isospecific sites, but also altered the stereochemical nature of the other active sites. Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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