Kinetic Behavior During Initial Stage (less than 1 s) of Propene Polymerization with Supported Catalyst

Keii, Tominaga; Terano, Minoru; Kimura, Kouhei; Ishii, Kotaro

doi:10.1007/978-3-642-83276-5_1

Cited by 15 publications

(2 citation statements)

References 8 publications

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“…The calculated barrier for the propagation reaction is Δ E # = 6.6 kcal/mol, and the inclusion of zero-point vibrational energy contributions, ZPE, slightly increases the calculated barrier (Δ E # ZPE = 7.3 kcal/mol). This value is in reasonable agreement with the value of the activation energy determined for propene polymerization with supported catalysts (Δ E # ≈ 9.5−12.0 kcal/mol) we checked the performance of our approach by calculating the activation energy for the catalytic model system in which the Mg 2 Cl 6 Ti part has been replaced with the Ti 3 Cl 8 part.…”

Section: Resultssupporting

confidence: 79%

Mechanisms of Propagation and Termination Reactions in Classical Heterogeneous Ziegler−Natta Catalytic Systems: A Nonlocal Density Functional Study

1998

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A nonlocal density functional study of ethylene polymerization with a model for the heterogeneous Ziegler−Natta catalyst is presented. We have considered the propagation as well as the termination reactions. In the absence of a coordinated olefin, the Ti−C (chain) σ bond does not occupy an octahedral coordination position but is oriented along an axis that is intermediate between the two octahedral coordination positions which are available. The propagation reaction occurs in a stepwise fashion, and the most favored mechanism requires a rearrangement of the growing chain out of the four-center transition-state plane. The insertion reaction is facilitated by a remarkable α-agostic interaction. The most favored termination reaction corresponds to the β-hydrogen transfer to the monomer. This reaction is favored relative to the C−H σ-bond activation of a coordinated monomer, as well as to the β-hydrogen transfer to the metal.

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Section: Resultssupporting

confidence: 79%

Mechanisms of Propagation and Termination Reactions in Classical Heterogeneous Ziegler−Natta Catalytic Systems: A Nonlocal Density Functional Study

1998

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“…In a standard preparation of a magnesium chloride/titanium chloride catalytic system, the milling process of MgCl 2 can produce different active surfaces on which the Ti can coordinate in several ways. − Since these Ti configurations can strongly differ in their stereoselective properties, the control of these surfaces is a crucial issue in tuning the polymer stereochemistry. Experimental investigations generally focus on the analysis of the polymer produced and correlations with the catalyst preparation are done at a second stage in order to recover a microscopic picture with the aid of model structures. − …”

Section: Introductionmentioning

confidence: 99%

A First Principles Exploration of a Variety of Active Surfaces and Catalytic Sites in Ziegler−Natta Heterogeneous Catalysis

et al. 2001

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We present a Car-Parrinello investigation of various active surfaces and catalytic sites in a realistic Ziegler-Natta heterogeneous system. We examine the (100), (110), and (104) surfaces of the MgCl 2 support and the related binding of the possible mononuclear and dinuclear catalyst configurations. Relaxation and/or reconstruction processes affect these surfaces in varying degrees, according to the different Miller indexes. We find that TiCl 4 and Ti 2 Cl 6 species can bind as stable adducts, depending on the morphology of the surface considered. However, the activation and polymerization phases show that destabilization phenomena can affect the dinuclear species during the catalysis reaction. This provides a new insight into the ability of the different centers to give rise to the real polymerization process. Finally, we present a first attempt to address the role of a typical donor phthalate at a fully first principles level.

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Surface acidic sites on supported titanium‐magnesium catalyst for propylene polymerization: ESR study via adsorption of stable nitroxyl radicals

Potapov¹,

Захаров²,

Mikenas³

et al. 1997

Macro Chemistry & Physics

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ESR was used for studying the interaction between the stable nitroxyl radical TEMPO (2,2,6,6-tetramethylpyperidin-1-oxyl) and the titanium-magnesium catalysts TiC14/MgC1, and TiC14/MgC12 * nD (D is either diisobutyl phthalate or 2,2-diisobutyl-l,3-dimethoxypropane), as well as TiC14/MgC12 -nD treated with triethylaluminium. In all cases, only part of the surface titanium complexes (18-53 mol-%) exhibit Lewis acid properties and can interact with TEMPO. The portion of titanium complexes with acidic properties depends on the composition and preparation of the catalysts, and it decreases upon treatment with triethylaluminium.

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Kinetic Behavior During Initial Stage (less than 1 s) of Propene Polymerization with Supported Catalyst

Cited by 15 publications

References 8 publications

Mechanisms of Propagation and Termination Reactions in Classical Heterogeneous Ziegler−Natta Catalytic Systems: A Nonlocal Density Functional Study

Mechanisms of Propagation and Termination Reactions in Classical Heterogeneous Ziegler−Natta Catalytic Systems: A Nonlocal Density Functional Study

A First Principles Exploration of a Variety of Active Surfaces and Catalytic Sites in Ziegler−Natta Heterogeneous Catalysis

Surface acidic sites on supported titanium‐magnesium catalyst for propylene polymerization: ESR study via adsorption of stable nitroxyl radicals

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