Kinetic studies on the pyrrole–Cr-based Chevron-Phillips ethylene trimerization catalyst system

The kinetics of the Ziegler-catalyzed polymerization of ethylene have been studied in a static system in the complete absence of any hydrocarbon vehicle. The apparatus which was developed consisted essentially of two mixing vessels, each of which was connected to the reaction vessel and to various manometric devices. Two mixtures were prepared: one of ethylene and aluminium trimethyl vapour and one of ethylene and titanium tetrachloride vapour. The fall in pressure due to the polymerization reaction was recorded. The dependence of the rate of polymerization on catalyst concentration and composition has been established. An optimum catalyst ratio was found at an Al/Ti mole ratio of 2:1. The rate of polymerization was concluded to be independent of the amount of aluminium trimethyl present over a large range of alkyl concentration. The kinetic order with respect to total pressure was found to be non-integral. It has been shown, moreover, that the effective catalyst concentration decreases during any given run. By employing a kinetic technique the effect of changing catalyst concentration has been removed and it has thus been demonstrated that the rate of polymerization is a linear function of catalyst and monomer concentration. It has been proved that diffusion of monomer through a polymer layer is not the rate-controlling process. The effect of added oxygen on the reaction rate has been investigated and the reaction was found to have a small positive temperature coefficient. The molecular weights of the polymers as a function of reaction conditions were determined using a viscometric procedure. The results are interpreted in terms of a physical mechanism of catalyst coverage by polymer and by a kinetic scheme. A titanium species is shown to participate in an important termination process; no evidence for chain transfer processes was forthcoming. A number of mechanisms which are compatible with the observed kinetics are tentatively proposed.

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The Study on the Reverse Atom Transfer Radical Polymerization of MMA Catalyzed by Acetylacetonate Cobolt(II) Complex Supported by Ionic Liquid

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.476-478.2188 ◽

2012 ◽

Vol 476-478 ◽

pp. 2188-2192

Author(s):

Jian Cai ◽

Tao Chen ◽

Guo Zhen Wang ◽

Jie Gao ◽

Rui Ma ◽

...

Keyword(s):

Ionic Liquid ◽

Methyl Methacrylate ◽

Atom Transfer Radical Polymerization ◽

Radical Polymerization ◽

1H Nmr ◽

Chemical Structure ◽

Kinetic Studies ◽

Catalyst System ◽

Polymerization Process ◽

Ft Ir

An ionic liquid supported catalytic system, chloromethylimidazole acetylacetonate Cobolt(Ⅱ) was successfully used in the RATRP of methyl methacrylate. The chemical structure of obtained PMMA was confirmed by FT-IR and 1H NMR. The polymerization process in the presence of ionic liquid was thoroughly investigated. The results revealed that this kind of initiator and catalyst system could promote RATRP of MMA with the desired characteristics, and the RATRP proceeded in a controlled manner as evidenced by kinetic studies.

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Titanium-based phenoxy-imine catalyst for selective ethylene trimerization: effect of temperature on the activity, selectivity and properties of polymeric side products

Catalysis Science & Technology ◽

10.1039/c9cy02056j ◽

2020 ◽

Vol 10 (6) ◽

pp. 1602-1608

Author(s):

Astrid Cordier ◽

Pierre-Alain Breuil ◽

Typhène Michel ◽

Lionel Magna ◽

Hélène Olivier-Bourbigou ◽

...

Keyword(s):

Kinetic Studies ◽

Effect Of Temperature ◽

Titanium Catalyst ◽

Thermal Switch ◽

Ethylene Trimerization

A thermal switch of selectivity for a phenoxy-imine titanium catalyst was studied by combining kinetic studies and a “polymer-to-catalyst” approach.

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The Effect of Substituents in PNPNH Ligands on Activity and Selectivity of a Chromium-Based Catalyst System for Highly Selective Ethylene Trimerization

ChemCatChem ◽

10.1002/cctc.201300324 ◽

2013 ◽

Vol 5 (10) ◽

pp. 3107-3113 ◽

Cited By ~ 11

Author(s):

Stefan Heinig ◽

Anina Wöhl ◽

Wolfgang Müller ◽

Mohammed H. Al-Hazmi ◽

Bernd H. Müller ◽

...

Keyword(s):

Catalyst System ◽

Effect Of Substituents ◽

Ethylene Trimerization

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Exploring Basic Components Effect on the Catalytic Efficiency of Chevron-Phillips Catalyst in Ethylene Trimerization

10.20944/preprints201804.0344.v1 ◽

2018 ◽

Author(s):

Ebtehal Naji-Rad ◽

Martí Gimferrer ◽

Naeimeh Bahri-Laleh ◽

Mehdi Nekoomanesh-Haghighi ◽

Roghieh Jamjah ◽

...

Keyword(s):

Density Functional ◽

Catalytic Efficiency ◽

Catalyst System ◽

Ethylene Oligomerization ◽

Side Reactions ◽

Phillips Catalyst ◽

Ethylene Trimerization ◽

Main Components ◽

Catalytic Cycles ◽

Work Effect

In the present work, effect of basic components on the energy pathway of ethylene oligomerization by landmark Chevron-Phillips catalyst has been explored in detail using density functional theory (DFT). Studied factors were chosen considering the main components of Chevron-Phillips catalyst, i.e. ligand, cocatalyst and halocarbon compounds, comprising i) the type of alkyl substituents in pyrrole ligand as methyl, iso-propyl, tert-butyl, and phenyl, as well as the simple hydrogen, and the electronwithdrawing fluoro and trifluoromethyl; ii) the number of Cl atoms in Al-compound (as AlMe2Cl, AlMeCl2 and AlCl3) which indicates halocarbon amount and iii) cocatalyst type as alkylboron, alkylaluminium, or alkylgallium. Besides main ingredients, solvent effect, from toluene or methylcyclohexane, on oligomerization pathway was explored as well. In this regard, the full catalytic cycles for the main product (1-hexene) formation as well as side reactions, i.e. 1-butene release and chromacyclononane formation, were calculated on the basis of the metallacycle based mechanism. Based on results, a modification on the Chevron-Phillips catalyst system, to reach higher 1-hexene selectivity and activity, is suggested.

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Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

Biochemical Society Symposium ◽

10.1042/bss0710001 ◽

2004 ◽

Vol 71 ◽

pp. 1-14

Author(s):

David Leys ◽

Jaswir Basran ◽

François Talfournier ◽

Kamaldeep K. Chohan ◽

Andrew W. Munro ◽

...

Keyword(s):

Electron Transfer ◽

Dimensional Space ◽

Three Dimensional ◽

Kinetic Studies ◽

Molecular Assembly ◽

Conformational Sampling ◽

Trimethylamine Dehydrogenase ◽

Key Residues ◽

Electron Transferring Flavoprotein ◽

Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

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