Metallocene Catalysts For Olefin Polymerization Research Articles

Structural Characterization and Spatial Mapping of Active Sites on Supported Metallocene Catalysts for Olefin Polymerization: A Luminescence-based Approach

Structural Characterization and Spatial Mapping of Active Sites on Supported Metallocene Catalysts for Olefin Polymerization: A Luminescence-based Approach

Ionic Liquid-Modified Porous Organic Polymers as Efficient Metallocene Catalyst Supports

Porous organic polymers (POPs) are widely used in various areas such as adsorption, separation and catalysis. In the present work, ionic liquid-modified porous organic polymers (IL-POPs) synthesized by dispersion polymerization were applied to immobilize metallocene catalysts for olefin polymerization. The prepared IL-POPs were characterized by Fourier transform infrared spectrometer (FT-IR), nitrogen sorption porosimetry, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometer (ICP) and scanning electron microscope (SEM) analysis. The IL-POPs obtained pores with surface specific area (SSA) ranging from 16.9 m2/g to 561.8 m2/g, and total pore volume (TPV) ranging from 0.08 cm3/g to 0.71 cm3/g. The supported catalysts Zr/MAO@IL-POPs exhibit great activity (3700 kg PE/mol·Zr·bar·h) in ethylene polymerization, and the GPC-IR results show that the polyethylene has narrow molecular weight distribution (2.2 to 2.8). The DSC results show that the melting point of prepared polyethylene was as high as 138 °C, and the TREF analysis results indicate that they have similar chemical composition distribution with elution temperature at 100.5–100.7 °C.

Single to Multiple Site Behavior of Metallocenes through C–H Activation for Olefin Polymerization: A Mechanistic Insight from DFT

Density functional theory has been used to study single to multiple site behavior of metallocene catalysts for olefin polymerization using (CpPr)2Hf(R)2 and (CpPr)2Zr(R)2 (here, R = Me and n-butyl ...

Preparation and characterization of agglomerated porous hollow silica supports for olefin polymerization catalyst

Self-prepared porous hollow silica (PHS) nanoparticles were agglomerated with an oil (kerosene)–ammonia method and used as a novel support of metallocene catalysts for olefin polymerization. Transmission electron microscopy (TEM), scanning electron microcopy (SEM), small-angle X-ray diffraction (SA-XRD) and nitrogen adsorption–desorption were employed to characterize the morphologies and mesostructures of the PHS particles and agglomerated PHS particles. It was found that the agglomerated PHS particles had an average diameter between 15 and 30μm, a specific surface area of 214m2/g, a pore diameter of 11–18nm and a pore volume of 1.41mL/g. Metallocene catalysts prepared with the agglomerated PHS as support demonstrated a very high activity of 8350g PE/gCata. for ethylene polymerization due to their particular morphology and mesostructures. Analysis with Differential Scanning Calorimetry (DSC), SEM, TEM and molecular weight analysis indicated that the polyethylene product was composed of tiny spherical particles with good crystalline and narrow molecular weight distribution, and the morphology and structure of the individual PHS support particle remained unchanged in polyethylene following the polymerization.

Non-Cp type homogeneous catalytic systems for olefin polymerization

Development of homogeneous metallocene catalysts for olefin polymerization has been briefly overviewed prior to detailed examination of the chemistry of non-Cp type homogeneous catalytic systems. In order to emphasize the structural characteristics of non-Cp catalysts, they were initially classified according to the coordination numbers of 4–7 and then further subclassified according to the ligand types. Over 100 line drawings and 200 references are utilized.

Synthesis of Silica-Supported Metallocene Catalysts for Olefin Polymerization

Four supported metallocene catalysts were synthesized directly on silica [Si(CpZrCp), Si(CpZrInd), Si(IndZrCp), and Si(IndZrInd)]. The first ligand was chemically tethered to silica (internal ligand) while the second was free from silica (external ligand). The polymerization of ethylene and the copolymerization of ethylene with hexene were investigated. The activity of the catalysts and the molecular weights of the polymers were found to depend on the position of the ligands. In all cases, high-molecular-weight polyethylene with moderate polydispersity was obtained. Moreover, the copolymerization of ethylene with hexene provided a homogeneous polymer. Reaction of ZrCl4(OC4H8)2 with modified silica (SiCp).

Preparation of isospecific metallocene catalysts for olefin polymerization that are covalently tethered on solid surface

Novel methodology was developed for preparation of isospecific metallocene catalysts for olefin polymerization that are tethered on silica surfaces with covalent bonds. A racemic ansa-zirconocene complex that has a Si–Cl moiety on its bridge was immobilized on SiO2 by the reaction of the Si–Cl anchor with Si–OH on the solid surface. The prepared solid catalyst was found to be effective for isospecific propene polymerization (catalyst A). Pretreatment of silica surfaces with Me3SiCl improved the catalyst performance (catalyst B). An ansa-zirconocene complex with a BH group reacted with “vinyl-coated” silica gel to afford another immobilized catalysts (catalyst C). This catalyst achieved satisfactorily high catalytic activity and high isotacticity in its produced polypropene.

Reactivity of Metallocene Catalysts for Olefin Polymerization: Influence of Activator Nature and Structure

In this review, various synthetic and structural aspects of methylaluminoxane and the elementary processes involved in olefin polymerization, as identified by various spectroscopic techniques, are detailed. Various boron-based counterions and their interactions with metallocenium cations are discussed. A comparison between MAO and boron-based activators in terms of catalytic activity and polymer characteristics is made. Finally, the use of the above system in the polymerization of cationically polymerizable monomers and acrylates is discussed.

Preparation and Characterization of MCM-41 Supported Metallocene Catalysts for Olefin Polymerization

The effect of the structure and surface properties of support material on metallocene (zirconocene chloride) adsorption and catalyst activity in ethene polymerization was studied. Commercial Grace silica, mesoporous silicate, MCM-41, and aluminium-modified MCM-41 were used as supports. The highest amount of zirconocene dichloride was adsorbed on Al-modified MCM-41 (Si/Al=32), providing the most reactive sites for attachment of the active component on the support surface. The 13C-CPMAS NMR studies proved that Cp2ZrCl2 is bound to the support surface. Also the highest activity in ethene polymerization was obtained using this support.

Metallocene catalysts for olefin polymerization: Annual review for 1996

This review covers research in olefin polymerization by metallocene catalysts published in 1996. While metallocenes are generally defined as metal complexes with two cyclopentadienyl rings, this review will additionally cover catalysts containing only one cyclopentadienyl ring, as well as catalysts with ligands isolobal to cyclopentadienide. Included will be certain disclosures concerning cocatalyst preparation and use. Polymer properties and uses will not be covered.

The heterogenization of homogeneous metallocene catalysts for olefin polymerization

Metallocene complexes of titanium, zirconium and hafnium are very active and versatile catalysts for olefin polymerization and are already contributing to commercial production. Owing to a variety of catalyst parameters a wide range of polymers with various properties are accessible. Since metallocene complexes are homogeneous in solution they can easily be studied by spectroscopic methods. However, for industrial application they must be heterogenized.

A semiempirical study of propylene adsorption on EtInd2ZrCH3 +/SiO2(111)

An Extended Huckel Method (ICONC) which includes core-core repulsion to the energy terms was used to characterize propylene adsorption on an active site model of SiO2-supported metallocene catalysts for olefin polymerization.

Highly active metallocene catalysts for olefin polymerization

The fascinating story of the discovery of the metallocene–methylaluminoxane catalysts for olefin polymerization is reviewed from its conception up until the first commercial production of polymers. A great number of different titanocenes and zirconocenes have been synthesized that give tailored polymers of totally different structures, and allows control of polymer tacticity, molecular weight and molecular weight distribution to be more efficient. New kinds of copolymers and elastomers can be synthesized.