Polymerization on Molecular Catalysts

Fink, Gerhard

doi:10.1002/9783527610044.hetcat0194

Cited by 7 publications

(5 citation statements)

References 204 publications

(152 reference statements)

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“…A dimeric hydride complex, [(2,4,7-Me 3 -Ind) 2 Y(µ-H)] 2 (17) (Scheme 5), appeared to be an effective catalyst for the homodimerization of various α-olefins [47]. The reaction was performed in benzene at 80-100 • C for 2-24 h, and there was a 20-50-fold molar excess of α-olefins.…”

Section: Catalytic Synthesis Of Terminal Alkene Dimers and Oligomersmentioning

confidence: 99%

“…Among the developing methods with significant potential for advancement and practical implementation is the catalysis of alkene dimerization and oligomerization using Ti subgroup metal salts and complexes, which provide high reaction rates and effective control of their chemo-, regio-, and stereoselectivity. The classical heterogeneous Ziegler–Natta catalysis is widely used in the production of polyethylene and polypropylene [ 16 , 17 , 18 , 19 , 20 , 21 ]. The discovery of metallocenes [ 22 ], along with organoaluminum [ 23 , 24 , 25 ] and boron activators [ 22 , 26 , 27 ], enabled the process to be transferred from a heterogeneous medium to a homogeneous one, which provided undoubted positive effects—such as an increase in the activity and the possibility to effectively control stereoselectivity—and allowed for a detailed study to be conducted on the reaction mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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The Dimerization and Oligomerization of Alkenes Catalyzed with Transition Metal Complexes: Catalytic Systems and Reaction Mechanisms

Parfenova,

Bikmeeva,

Kovyazin

et al. 2024

Molecules

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Dimers and oligomers of alkenes represent a category of compounds that are in great demand in diverse industrial sectors. Among the developing synthetic methods, the catalysis of alkene dimerization and oligomerization using transition metal salts and complexes is of undoubted interest for practical applications. This approach demonstrates substantial potential, offering not only elevated reaction rates but also precise control over the chemo-, regio-, and stereoselectivity of the reactions. In this review, we discuss the data on catalytic systems for alkene dimerization and oligomerization. Our focus lies in the analysis of how the activity and chemoselectivity of these catalytic systems are influenced by various factors, such as the nature of the transition metal, the ligand environment, the activator, and the substrate structure. Notably, this review particularly discusses reaction mechanisms, encompassing metal complex activation, structural and dynamic features, and the reactivity of hydride intermediates, which serve as potential catalytically active centers in alkene dimerization and oligomerization.

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Section: Catalytic Synthesis Of Terminal Alkene Dimers and Oligomersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Dimerization and Oligomerization of Alkenes Catalyzed with Transition Metal Complexes: Catalytic Systems and Reaction Mechanisms

Parfenova,

Bikmeeva,

Kovyazin

et al. 2024

Molecules

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show abstract

“…[ 7,9 ] For industrial use, metallocene catalysts are usually supported on amorphous silica gel with micrometer size and porous structure, in order to produce polymer particles with uniform morphology and high bulk density and to prevent fouling problem inside polymerization reactors. [ 10‐12 ] It is very hard to maintain uniform polymer particle morphology because of the breakup of commercially silica gels during polymerization. [ 11 ]…”

Section: Introductionmentioning

confidence: 99%

“…[ 10‐12 ] It is very hard to maintain uniform polymer particle morphology because of the breakup of commercially silica gels during polymerization. [ 11 ]…”

Section: Introductionmentioning

confidence: 99%

Formation of uniform polymer assembly with silica nano‐sol‐supported metallocene catalysts in a stirred‐tank reactor

Yang

2021

Polymer Engineering & Sci

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Silica nano‐sol is the precursor (before gelation and drying) of silica gel and has much greater surface area than gel. In this study, a spherical commercial silica nano‐sol in toluene with a dimension of less than 50 nm was successfully used to support two bridged metallocenes (dicholo ‐ dimethyl silybis(indenyl) zirconium (IV) and dichloro – ethylenebis(indenyl) zirconium (IV),denoted by ZrSi and ZrEt, respectively). These sol‐supported catalysts showed significantly better propylene polymerization activities than gel‐supported catalyst reported earlier. The influences of solution co‐catalyst ([Al4O3Me6]n, n = 5–7, abbreviated as MAO) content and reaction time on polymerization were investigated. The increase of co‐catalyst concentration increased activity, polymer length, and melting temperature. Polymer assemblies produced with ZrSi/Sol changed from diamond‐shape to rod‐like shape as time proceeded. Uniform dumbbell – shaped micro‐sized polypropylene assemblies were obtained with catalyst ZrEt/Sol. The results were explained in terms of the penetration theory proposed before for multiphase mass transfer.

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“…In order to produce morphologically uniform polymer particles with high bulk density and to avoid reactor fouling, industrial metallocene catalysts have to be supported on a MAO-modified solid carrier (so-called drop-in catalysts) [8]. Micro-sized amorphous and porous silica is most commonly used for supporting metallocence/MAO catalysts because of its high surface area/porosity, good mechanical properties, and fine stability under reaction and processing conditions [9,10].…”

Section: Introductionmentioning

confidence: 99%

Propylene Polymerization Catalyzed by Metallocene/Methylaluminoxane Systems on Rice Husk Ash

Yang

2019

Molecules

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Silica generated from agricultural waste is more cost effective and environmentally friendly than silica from traditional commercial processes. In this study, spherical silica particles with a diameter of around 120 nm were fabricated from rice husk ash (RHA), and were used to support two bridged zirconcene complexes ((I) Me2Si(Ind)2ZrCl2 and (II) C2H4(Ind)2ZrCl2 ) for catalyzing propylene polymerization to produce polypropylene (PP) in a temperature range of 40–70 C and in a solution methylaluminoxane (MAO) range of 0.1–0.6 wt%. Due to its small particle size, RHA-supported catalyst exhibited much higher activity than micro-sized commercial silica-supported catalyst. At the optimum polymerization temperature of 55 C and with increasing MAO concentration, polymer yield increased proportionally with the increase of number average molecular weight. Compared to (I), (II) produced more polymer molecules but with much shorter chain length, ascribed to the differences of Zr loading and bridge structure. With increasing polymerization temperature, polymer molecular weight decreased rapidly and resulted in a significant change of PP assembly morphology (shape and size). At 55 C, (I) produced uniform PP assemblies which had dumbbell-like structure with a smooth middle section and two fibrillar ends, while (II) produced spherical PP particles. The dumbbell middle part width was essentially identical to the Batchelor microscale proposed in turbulent mixing theory.

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Polymerization on Molecular Catalysts

Cited by 7 publications

References 204 publications

The Dimerization and Oligomerization of Alkenes Catalyzed with Transition Metal Complexes: Catalytic Systems and Reaction Mechanisms

The Dimerization and Oligomerization of Alkenes Catalyzed with Transition Metal Complexes: Catalytic Systems and Reaction Mechanisms

Formation of uniform polymer assembly with silica nano‐sol‐supported metallocene catalysts in a stirred‐tank reactor

Propylene Polymerization Catalyzed by Metallocene/Methylaluminoxane Systems on Rice Husk Ash

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