John C. Chadwick

• Independent Researcher

This article comprises an updated overview of magnesium chloride-supported catalysts for polypropylene, covering historical developments, mechanistic insight, and the effect of the catalyst on polymer structure.

The activity and stability of homogeneous olefin polymerisation catalysts, when immobilised on a support, are dependent on both chemical and physical effects. Chemical factors affecting catalyst activity include the ease of formation of the active species, which is strongly dependent on the transition metal. Catalyst productivity is dependent on th...

Transmetallation of 4,4'-bis{(2,6-bis[(dimethylamino)methyl]phenylgold)diphenyl-phosphino}biphenyl (3) with MCl(4) (M = Ti, NbCl, V) in benzene gave the corresponding transition metal pincer complexes (4) and insoluble 4,4'-bis[P-(chloro gold(I))diphenylphosphino]biphenyl (2), which can be quantitatively recovered and recycled. Interestingly, 3 did...

This first book to illuminate this important aspect of chemical synthesis improves the lifetime of catalysts, thus reducing material and saving energy, costs and waste. The international panel of expert authors describes the studies that have been conducted concerning the way homogeneous catalysts decompose, and the differences between homogeneous...

Reaction of (S,S)-2,6-bis(4′-isopropyl-2′-oxazolinyl)phenyllithium (i-Pr-Phebox-Li) (2a) with 4,4′-bis[P-(chlorogold(I))diphenylphosphino]biphenyl [(dppbp)(AuCl)2] (5) afforded the new, bimetallic gold complex 4,4′-bis[P-(η1-C-i-Pr-Phebox-gold)diphenylphosphino]biphenyl [(P-Au(η1-C-i-Pr-Phebox))2(dppbp)] (6). Transmetalation of 6 with 2 equiv of Cl...

Bimodal polyethylenes comprising varying proportions of high‐ and low‐molecular‐weight fractions are synthesized in a single polymerization stage, via the co‐immobilization of a chromium and an iron catalyst on an MgCl 2 /AlEt n (OEt) 3− n support. Changes observed in the viscoelastic response of the polymer melt with increasing content of the high...

This Essay inaugurates a Special Article Series called Polyolefins Catalyst and Process Innovations. Examples illustrating recent progress in both the fundamental understanding and application of Ziegler-Natta and single-centre catalysts in polyolefin production are given, notably in relation to the effect of catalyst and process modification on po...

A sensitive method is presented for the investigation of planar Ziegler-Natta model catalysts by means of attenuated total internal reflection Fourier transform infrared spectroscopy. A solution of MgCl2 in ethanol, optionally containing an internal donor, was spin-coated directly onto a planar ZnSe ATR crystal. Ethylene and propylene polymerizatio...

The ability of a MgCl 2 support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily ef...

An active model for a Ziegler–Natta propylene polymerization catalyst has been prepared by spin-coating of a MgCl2/diether donor solution in ethanol on a flat silicon wafer, followed by crystal growth by Ostwald ripening to give well-defined MgCl2⋅donor⋅nEtOH crystallites. The growth of the crystallites on the flat wafer indicates the formation of...

This first comprehensive handbook on this exciting field provides readers with a clear understanding of the current state of the art, ingenious solutions and opportunities. Researchers from academia and industry present such emerging topics as multi-component systems and computational chemistry, as well as the latest developments in competing and c...

IntroductionMagnesium Chloride as ActivatorMagnesium Chloride/MethylaluminoxaneMagnesium Chloride/BorateMagnesium Chloride/Aluminum Alkyl Early-Transition Metal ComplexesLate-Transition Metal ComplexesConclusions References Early-Transition Metal ComplexesLate-Transition Metal Complexes

We make use of a specially synthesized linear high density polyethylene with a bimodal molecular weight distribution (MWD) to demonstrate that it is possible to produce a suspension of extended-chain (shish) crystals only. Such a suspension can be generated at high temperatures, above but close to the equilibrium melting temperature of the unconstr...

The effect of cyclopentadienyl ring substitution on the immobilization and activation of zirconocenes on supports of type MgCl2/AlRn(OEt)3-n has been investigated. Comparison of the activity of immobilized zirconocenes (RCp)2ZrCl2 in ethylene polymerization, using simple aluminum alkyls such as AlEt3 or AliBu3 as a cocatalyst, revealed a remarkable...

An active model for a Ziegler-Natta propylene polymerization catalyst has been prepared by spin-coating of a MgCl2/diether donor solution in ethanol on a flat silica wafer, followed by crystal growth by Ostwald ripening to give well-defined MgCl2 · diether · nEtOH crystallites. The flat model approach facilitates detailed characterization of the ca...

Immobilization of combinations of early- and late-transition metal catalysts on MgCl2 supports has led to significant increases in catalyst activity when a nickel diimine is incorporated into a Fe-, Cr- or Ti-based catalyst system, and to the formation of intimately mixed, bimodal blends of high- and low-molecular weight polyethylene via coimmobili...

All polymerization experiments were carried out in a Büchi glass reactor capable of operating at propylene pressures of 1-7 atmospheres. Two types of MgCl2 supported catalysts with controlled morphology were studied, viz., catalyst systems containing either a 1,3 diether (Catalysts A and D), 9,9-bis (methoxymethyl) fluorene, or a simple diester (Ca...

Investigation of the melt rheological properties of polyethylenes prepared with chromium, titanium, vanadium, and zirconium catalysts immobilized on MgCl2 supports has confirmed narrow (Schulz−Flory) molecular weight distribution, indicative of single-center catalysis, for Cr-, V-, and Zr-based systems, but not for Ti. In the case of polymers prepa...

The effects of hydrogen in ethylene polymerization and oligomerization with different bis(imino)pyridyl iron(II) complexes immobilized on supports of type MgCl2/AlEtn(OEt)3–n have been investigated. Hydrogen has a significant activating effect on polymerization catalysts containing relatively bulky bis(imino)pyridyl ligands, but this is not the cas...

A method for the preparation of well‐defined crystallites of MgCl 2 ‐supported Ziegler‐Natta catalysts on Si wafers has been developed. This has been achieved by the spin‐coating of a MgCl 2 solution onto a flat Si wafer, followed by controlled crystal growth to give well‐defined MgCl 2 · n EtOH crystallites. The growth of the crystallites on the f...

Cover: The cover picture describes a method for the preparation of well‐defined crystallites of MgCl 2 ‐supported Ziegler‐Natta catalysts on Si wafers. The growth of the crystallites on the flat silica facilitates their characterization using Electron and Scanning Probe Microscopy. The relative proportions of 120° and 90° edge angles indicate the p...

Significant increases in the productivity of iron-, chromium-, and titanium-based MgCl2-supported catalysts for ethylene polymerization have been obtained by incorporation of a limited amount of a nickel diimine catalyst giving branched polyethylene. Formation of the latter during the early stages of polymerization reduces the monomer diffusion lim...

An active model for a Ziegler–Natta ethylene polymerization catalyst has been prepared by spin-coating of a MgCl2 solution in ethanol on a flat silicon (100) substrate covered by amorphous silica. The flat model approach facilitates characterization of the catalyst using surface spectroscopy and microscopy techniques. This model catalyst features a...

The influence of cooling rate from the melt on the polymorphism and crystallinity is investigated as a function of isotacticity and stereo-defect distribution in polypropylenes. Detailed analysis of wide angle x-ray diffraction patterns shows that crystallinity in the materials used is nearly independent of the experimental cooling rates (0.5–40°C/...

Ethylene polymerizations carried out with various bis(imino)pyridyl iron, chromium and vanadium complexes immobilized on a MgCl2/AlRn(OEt)3−n support gave relatively broad polyethylene molecular weight distributions in the case of iron, but high molecular weight and a very narrow molecular weight distribution with vanadium, indicative of a single a...

The impacts of propylene prepolymerization on ethylene/1-hexene and ehylene/1-octene copolymerization studies carried out with a catalyst comprising a zirconocene and MAO immobilized on a silica support were analyzed. The copolymerization of samples, following the prepolymerization, was carried out by the charging of the desired amount of the comon...

This article describes the quantitative aspects of the isoselectivity distribution of isospecific centers in five supported titanium‐based Ziegler–Natta catalyst systems containing different internal and external organic donors. Highly crystalline poly(propylene) fractions of the polymers (insoluble in o ‐xylene at 95 °C) were analyzed by analytica...

An investigation of the polymer particle growth characteristics and polymer molecular weight and composition distributions in ethylene homopolymerization and ethylene/1-hexene copolymerization has been carried out with a catalyst comprising a zirconocene and methylaluminoxane immobilized on a silica support. The presence of 1-hexene leads to higher...

Active center determinations on different Ziegler–Natta polypropylene catalysts, comprising MgCl2, TiCl4, and either a diether or a phthalate ester as internal donor, have been carried out by quenching propylene polymerization with tritiated ethanol, followed by radiochemical analysis of the resulting polymers. The purpose of this study was to dete...

New approaches have been identified for the immobilization, on a MgCl2-based support, of borate activators for metallocene-catalyzed olefin polymerization. Immobilization of [HNEt3][B(C6F5)3(C6H4-4-OH)] was carried out by reaction with a support of type MgCl2/AlRn(OEt)3−n, obtained by reaction of AlEt3 with an adduct of magnesium chloride and ethan...

Immobilization and activation of a broad range of titanium-, chromium-and nickel-based single-site catalysts for ethylene polymerization has been carried out using supports of type MgCl2/AlRn(OEt)3 − n , prepared by reaction of AlR3 with adducts of magnesium chloride and ethanol. The spherical particle morphology of the support is retained and repl...

The use of tri iso butylaluminium and diethyl zinc as cocatalyst and chain transfer agent respectively in ethylene/1‐hexene copolymerisation, carried out with a Ziegler‐Natta catalyst of type MgCl 2 /TiCl 4 /di iso butyl phthalate, has been found to give significantly higher comonomer incorporation than was obtained when triethylaluminium was used...

Immobilized single-site polymerization catalysis has been the subject of several reviews in both length and scope. The present review comprehensively covers the substantial body of research within this field, focusing particularly on the requirements, challenges, protocols, and ingenious solutions to the successful immobilization of single-site cat...

Investigation of the characteristics and performance in propylene polymerization of silica-immobilized methylaluminoxane (MAO), in combination with a moderately and a highly isospecific zirconocene catalyst, has revealed that a simple impregnation of silica with MAO at ambient temperature is insufficient to obtain uniform distribution of MAO throug...

Significant increases in the activity of vanadium(III) amidinate catalysts for ethylene polymerization have been obtained by immobilization on a MgCl2-based support prepared by reaction of AlEt3 with a MgCl2/ethanol adduct. Catalyst immobilization and activation on this type of support prevents the rapid decay in activity observed under homogeneous...

Polymer particle growth in the early stages of olefin polymerization has been investigated using metallocene/methylaluminoxane (MAO)/silica catalyst systems. Scanning electron microscopy (SEM) has been used to characterize the surface and cross-sectional morphology of polymer particles at different stages of particle growth. The aluminum distributi...

The effective immobilization and activation of a single‐site chromium catalyst for ethylene polymerization has been achieved using MgCl 2 /AlR n (OEt) 3 − n supports, without the use of methylaluminoxane (MAO) or a borate activator. High catalyst activity and a spherical polyethylene‐particle morphology is obtained. Furthermore, the single‐site cha...

Fundamental implications of occasional secondary (2,1-) insertions in propene polymerization with different MgCl2-supported Ziegler−Natta catalysts are discussed, with reference to the properties of the polymers obtained. The relatively narrow molecular weight distribution of polypropylene prepared using catalysts of type MgCl2/TiCl4/diether−AlR3 i...

Easy and effective immobilization and activation of a range of Ti‐based single‐site catalysts for ethylene polymerization has been achieved, without methylaluminoxane or borate activators, using MgCl 2 /AlR n (OEt) 3– n supports obtained by reaction of AlR 3 with adducts of magnesium chloride and ethanol. The use of relatively low catalyst loadings...

Front Cover: High and stable activity in ethylene polymerization has been achieved with a wide range of Ti‐based single‐site catalysts without the use of MAO or borate activators, using spherical supports of type MgCl 2 /AlR n (OEt) 3– n obtained by reaction of AlR 3 with adducts of MgCl 2 and ethanol. Polyethylene having spherical particle morphol...

The propene/ethene-[1-13C] copolymerization method has been applied to measure precisely the regioselectivity of two modern MgCl2-supported Ziegler−Natta catalyst systems for the industrial production of isotactic polypropylene, namely MgCl2/di(isobutyl)-o-phthalate/TiCl4−cyclohexylmethyldimethoxysilane/AlR3 (1) and MgCl2/2,2-di(isobutyl)-1,3-dimet...

The immobilization and activation of nickel diimine catalysts using MgCl2-based supports were analyzed. The catalyst immobilization was carried out by mixing the support with toluene solution of catalyst and reacting at 50°C for 4h. The melting points of polymers indicated different levels of chain branching which were determined by DSC. THe SEM im...

Supports of type MgCl 2 /AlR n (OEt) 3− n , obtained by reaction of AlR 3 with adducts of MgCl 2 and ethanol, have been shown to be effective for the immobilization and activation of [Cp 2 TiCl 2 ] and other single‐site olefin polymerization catalysts without the use of methylaluminoxane or a borate activator. Polyethylene with a spherical particle...

Cover: Effective immobilization and activation of Cp 2 TiCl 2 and other single‐site olefin polymerization catalysts has been achieved using spherical supports of type MgCl 2 /AlR n (OEt) 3‐ n , obtained by reaction of AlR 3 with adducts of MgCl 2 and ethanol. Polyethylene having spherical particle morphology and narrow molecular weight distribution...

The propene/ethene-[1-13C] copolymerization method has been applied to measure precisely the regioselectivity in propene polymerization of the “simple” MgCl2/TiCl4 catalyst (activated with Al(iBu)3), which can be viewed as the ancestor of all present-day MgCl2-supported industrial catalysts containing Lewis bases as selective modifiers. It has been...

This article describes the development and characteristics of Ziegler–Natta catalysts for the polymerization of ethylene, propylene, and other alpha-olefins. Particular emphasis is given to state-of-the-art MgCl2/TiCl4/donor catalysts for polypropylene, including current insight into mechanistic aspects of Ziegler–Natta catalysis in relation to cat...

The fundamental factors determining the performance of state-of-the-art MgCl2-supported catalysts for polypropylene are becoming increasingly evident. Polymer yield, isotacticity, molecular weight and molecular weight distribution are dependent on the regio- and stereoselectivity of the active species. Chain transfer with hydrogen after the occasio...

Poly(propylene)s prepared using MgCl2-supported catalysts containing different electron donors have been characterized using temperature rising elution fractionation (TREF), gel permeation chromatography (GPC) and 13C NMR analysis. In addition, the regio- and stereochemical composition of oligomeric fractions present in selected polymers has been d...

Poly(propylene)s prepared using MgCl2-supported catalysts containing different electron donors have been characterized using temperature rising elution fractionation (TREF), gel permeation chromatography (GPC) and 13C NMR analysis. In addition, the regio- and stereochemical composition of oligomeric fractions present in selected polymers has been d...

13C and 1H NMR analysis of polypropylene prepared using various MgCl2-supported catalysts at different polymerization temperatures at different hydrogen concentrations has revealed that chain transfer with monomer, yielding vinylidene-terminated chains, is essentially unaffected by hydrogen but is dependent on catalyst selectivity. Chain transfer w...

Studies on the effects of hydrogen, monomer concentration and temperature in propene polymerization using high-activity MgCl2-supported catalysts have revealed that the effects of the catalyst on polymer yield, isotacticity and molecular weight are interrelated and dependent on both regio-and stereoselectivity. The high hydrogen sensitivity of cata...

The stereosequence distribution of the “atactic” and “isotactic” fractions of a polypropylene sample made with a MgCl2-supported catalyst was determined by means of high-resolution 13C NMR and analyzed in terms of statistical models of increasing sophistication. Two-site models, including the one normally used for the interpretation of “routine” 13...

Polypropylene is one of the most versatile and successful materials in the market because of the ever-increasing spectrum of polymer composition and properties which have originated from continuing breakthroughs in catalyst and process technology. Industrial polypropylene production is based on Ziegler-Natta supported catalysts. The success of MgCl...

The configurational analysis of polypropylenes made with coordination catalysts has received a tremendous impulse by the recent application of high-field 13C NMR techniques. In particular, unprecedented determinations of stereosequence distribution at heptad/nonad level have made more realistic and sophisticated models of chain propagation applicab...

A study of the effect of polymerization temperature on the microtacticity of poly(propylene) prepared using various MgCl2-supported catalysts has shown that, in almost all cases, an increase in temperature leads not only to higher proportions of isotactic polymer but also to increased stereoregularity of the isotactic fraction. The results indicate...

The behavior in propylene polymerization of divalent titanium compounds of type [η6-areneTiAl2Cl8], both as such and supported on activated MgCl2, has been studied and compared to that of the simple catalyst MgCl2/TiCl4. Triethylaluminium was used as cocatalyst. The Ti–arene complexes were active both in the presence and in the absence of hydrogen,...

1-Butene polyinsertion promoted by two typical C2-symmetric zirconocene catalysts (i.e. rac-ethylenebis(1-indenyl)ZrCl2 (1) and rac-dimethylsilylbis(1-indenyl)ZrCl2) (2) was investigated under both hydrooligomerization and polymerization conditions and compared with that of propene. It was found that, in spite of a similar regiospecificity for the...

13C NMR analysis of poly(propylene) fractions of different tacticity, obtained using a catalyst system of type MgCl2/TiCl4/diisobutyl phthalate – AlEt3 – diether, has provided further evidence that the active species in this system are similar to those in which the ether is used as “internal” rather than “external” donor. Chain-end analysis of rela...

3-Methyl-1-butene was polymerized in the presence of a number of homogeneous metallocene catalysts (co-catalyst methylalumoxane). Contrary to literature reports, it was found that even the simplest C2-symmetric metallocenes promote the isotactic polymerization of this monomer with reasonable productivities. Quite surprisingly, a prevailingly isotac...

13C NMR analysis of the chain-end distribution of poly(propylenes) prepared using the highly active catalyst system MgCl2/TiCl4/diether—AlEt3 has revealed particularly high proportions of butyl chain-ends in polymers prepared at relatively low hydrogen pressures. This indicates that the high sensitivity of this type of catalyst to hydrogen, both wi...

Investigation of the effects of hydrogen and different external donors on the stereoregularity and chain-end distribution of polypropylene prepared using MgCl2/TiCl4/phthalate ester-AlEt3-alkoxysilane catalyst systems has not only confirmed the importance of regiospecificity in relation to hydrogen activation but has also indicated a significant ef...

Electron donors play a dominant role in determining the behavior of super high activity (MgCl2-supported) catalysts for polypropylene. This is particularly so in systems in which the internal donor is a phthalate ester and where an alkoxysilane or hindered amine is used as external donor. Fundamental questions pertaining to the mechanism of these c...

The effects of regiochemical and stereochemical errors on the kinetic course of isotactic propene polyinsertion promoted by two typical homogeneous metallocene catalysts are analyzed in detail. It is shown, in particular, that occasional regioirregular 2,1 insertions not only slow down chain propagation to a substantial extent-as already reported i...

13C NMR analysis of relatively low-molecular-weight polypropylenes prepared using the catalyst system MgCl2/TiCl4/phthalate ester-AlEt3-external Lewis base has revealed the presence of up to around 20% butyl (n-Bu) chain ends, indicative of regioirregular (2,1-) monomer insertion followed by chain transfer with hydrogen. The effect of hydrogen on c...

Possible propagation mechanisms in propene polymerization using heterogeneous catalysts are described by combinations of Bernoulli and first‐ or even second‐order Markov models. Both NMR‐measured pentad fractions and GPC Gel permeation chromatography. ‐measured molecular weight distributions are directly taken into account to fit an appropriate pro...

A new method is presented for data reconciliation in the 13C NMR determination of the pentad distribution in regioregular poly(propylene). Deviations of experimentally measured data from mathematically derived conservation laws are corrected by a maximum-likelihood method. In this method some assumptions are made about the structure of the erros to...

In propylene polymerization with MgCl2/TiCl4/phthalate ester catalysts, using 2,2,6,6-tetramethylpiperidine as external donor, it has been found that the fraction of atactic polymer formed increased with decreasing ester content in the catalyst. At the same time, however, the stereoregularity of the isotactic polymer fraction, as measured by 13C NM...

The properties of elastomers are dependent on the configuration and distribution of monomer units in the polymer chain and on variables such as molecular weight and degree of branching. This article describes the correlation between elastomeric properties and factors such as glass transition temperature and crystallinity, and illustrates how the st...