Ziegler-Natta Research Articles

Effects of Silica Support Properties on the Performance of Immobilized Metallocene Catalysts for Ethylene Polymerization

AbstractThe choice of the silica support for α‐olefin polymerization catalysts has overwhelming ramifications on the overall metal loading, catalyst performance, and properties of the resulting polymer. There are several physical properties of a silica support to consider but the pore volume and pore diameter are the two of the most important support properties in such considerations. During the catalyst immobilization process and the subsequent polymerization reaction, the change in the pore volume can either facilitate or inhibit the mass transfer of catalytic compounds and monomers within and throughout the catalyst particle. This work presents the experimental study on the effects of pore diameter and pore volume in porous silica particles used to support rac‐Et(ind)2ZrCl2 catalyst on ethylene polymerization. The amount of immobilized methylaluminoxane (MAO) is varied for three commercially available silica micro‐particles with similar surface areas and particle sizes. It has been observed that each type of silica exhibits different effects of the immobilized MAO on their pore characteristics, although a general trend is observed. Ethylene polymerization in slurry phase with the prepared supported catalysts also shows that the polymerization activities can be correlated with pore diameter and surface area for the three silica supports.

Physical Properties of Isotactic Polypropylene Blended with Less Crystalline Polypropylene

AbstractThe physical properties of polymeric materials, which are mixtures of various molecules, are determined by the sum of their contributions. Industrially important isotactic polypropylene (iPP), which is produced using heterogeneous Ziegler–Natta catalysts, shows broader distributions of molecular weight and stereoregularity because of the multisite nature, compared to molecular catalysts. However, systematic studies on the effects of these distributions on physical properties are lacking, especially for variations in stereoregularity. In this study, polypropylene (PP) additives with various molecular weights and stereoregularities (and their distributions) are added to an iPP matrix to clarify the effects of low‐concentration components on the overall physical properties. The results indicate the importance of incorporating the PP additives into the crystal structure of the iPP matrix.

Impact polypropylene copolymers containing multifold H-shape long-chain-branching structures: Synthesis and properties

ω -Alkenylmethyldichlorosilane as a proven in-situ long-chain-branching agent particularly effective with olefin polymerization by Ziegler-Natta catalysts was seamlessly fit into fully implemented impact copolymerization of propylene exercised by polymerization, steam-treatment of afforded polymer granules, and twin-screw extrusion in a row to deliver, for the first time, long-chain-branched impact polypropylene copolymers (LCB-IPCs). Multifold H-type LCB structures were revealed with the LCB-IPCs, including two homologous structures based on polypropylene (PP- H -PP) and ethylene-propylene copolymer (EPC- H -EPC) individually, and a heterologous structure mixed of PP and ethylene-propylene copolymer (PP– H -EPC). Though all in minute amount, the LCB structures induced significant improvement in IPCs on many fronts. On melt properties, LCB-IPCs gained the unprecedented strain hardening property in extensional flow. On phase morphology, the LCB structures helped reduce the dispersion dimension of ethylene-propylene copolymer and the tendency of grain coarsening in post-preparation processing. On melt crystallization, the LCB structures enhanced the crystallization in an all-round way by prompting self-nucleation. On mechanical properties, by reinforcing the PP matrix and strengthening the interface to facilitate stress transfer between PP and EP copolymer, the LCB structures enabled an all-out promotion of mechanical properties with simultaneous reinforcement on stiffness and toughness. Fully implemented impact copolymerization of propylene preparing impact polypropylene copolymers was engaged with LCB agent 5-hexenylmethyldichlorosilane, which prompted formation of multifold H-shape LCB structures in the copolymers. The multifold LCB structures in turn induced profound improvement on multiple fronts of the copolymer properties. • ω -Alkenylmethyldichlorosilane is used as a LCB agent in impact copolymerization of propylene. • The new IPC polymers contain multifold H-type LCB structures. • The LCB structures induced significant improvement in properties of IPC on many fronts.

Unity Makes Strength: Constructing Polymeric Catalyst for Selective Synthesis of CO 2 /Epoxide Copolymer

Unity Makes Strength: Constructing Polymeric Catalyst for Selective Synthesis of CO ₂ /Epoxide Copolymer

Understanding the Role of Sulfonyl Amine Donors in Propylene Polymerization Using MgCl2-Supported Ziegler–Natta Catalyst

Ziegler–Natta catalysts are one of the mainly used industrial catalysts for the large-scale production of polyolefins. As one of the important components in a Ziegler–Natta catalyst, the internal donor and external donor pair is responsible for increasing the stereoregularity of polypropylene. In this work, a series of sulfonyl amine internal donors were systematically investigated by density functional theory (DFT) calculations. The adsorption behavior of the sulfonyl aromatic amine BTFMSPA-m-Cl indicates that the O atom exhibited an excellent coordinating affinity to the 4-coordinated Mg atoms on the MgCl2(110) surface among the three functional atoms (F, Cl, O). In addition, the substituents have a great influence on the adsorption behavior of the sulfonyl amines. The functional atom of the substituent (Cl or OMe) in the phenyl ring and the oxygen of the sulfonyl group tend to form a more stable bridge-coordination (Cl-Mg1,Mg2-O3, or O-Mg1,Mg2-O3) than the chelate-coordination (O1-Mg2-O2). In all considered internal donors, the stereoselectivity of the Ti active site can be greatly enhanced in the presence of BTFMSPA-m-Cl, which presumably results from the steric hindrance around the Ti active site caused by the bridge-coadsorbed BTFMSPA-m-Cl.

Exploring cocatalyst type effect on the Ziegler–Natta catalyzed ethylene polymerizations: experimental and DFT studies

Due to the important role of cocatalyst in the polymerization process employing industrially favored Ziegler–Natta catalysts, its effect on kinetic behavior, catalyst activity, and polymer properties is discussed. In this paper, triethyl aluminum (TEA) and triisobutyl aluminum (TIBA) have been used as the main cocatalyst ingredient with 10–20 mol percent of diethyl aluminum chloride (DEAC) and ethyl aluminum dichloride (EADC) cocatalysts, being neat TEA the cocatalysts with the highest activity. Moreover, TEA-DEAC and TEA-EADC cocatalysts revealed a built-up kinetic profile, while TIBA-DEAC and TIBA-EADC show a decay-type kinetic curve. According to melt flow index results, no considerable change in flowability was detected in the synthesized polyethylenes (PE). On the other hand, the ethylene insertion and chain termination mechanisms were investigated by means of density functional calculations using Ti active center located in (110) and (104) facets of the MgCl2 surface. To shed light on the bulkiness level of employed cocatalysts, buried volume (VBur) together with the two-dimensional map of cocatalyst systems were considered. Higher VBur of TIBA complex can explain its lower activity and decay type kinetic profile obtained by experimental studies.

Nitrogen Poisoning of HDPE and LLDPE based on Chemically Recycled Post‐Consumer Plastic via a Kinetic and Microstructural Modeling Technique

AbstractChemical recycling of plastic waste has promise as a complementary technology to increase eco‐efficiency of plastics life cycles. Accumulation of impurities in feed streams can affect sensitive compounds such as the Ziegler–Natta catalyst systems commonly used to produce polyolefins such as high density polyethylene (HDPE) and linear low density polyethylene (LLDPE). In a poison study, the influence of impurities—more specifically NO and N2O—on the catalyst system are investigated comprehensively in terms of kinetic behavior and activity rates. A product composition analysis gives insights into product properties such as molecular weight distribution (MWD), comonomer composition distribution (CCD), melting point, and crystallinity. By applying known modeling techniques (kinetic modeling, MWD, and CCD deconvolution modeling), information beyond analytical data is obtained. The results of the study show that both poisons significantly affect catalyst kinetics and reduce catalyst activity. N2O influences primarily the MWD, while NO poisoning strongly affects the CCD of LLDPE samples. Since the mechanical properties of the polymers produced depend on factors such as MWD and CCD, NO and N2O poisoning may reduce their processability and applicability.

CSPC, SCPC expand cooperation to develop HDPE and metallocene catalysts products

CSPC, SCPC expand cooperation to develop HDPE and metallocene catalysts products

Investigation of Optimal Condition of Ethylene Polymerization Using a New Three-Metallic High-Performance Ziegler–Natta Catalyst: Experimental Design and Polymer Characterization

Investigation of Optimal Condition of Ethylene Polymerization Using a New Three-Metallic High-Performance Ziegler–Natta Catalyst: Experimental Design and Polymer Characterization

Melting Temperature Depression of Polymer Single Crystals: Application to the Eco-Design of Tie-Layers in Polyolefinic-Based Multilayered Films.

In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to define the molecular characteristics of the polyolefinic structural layer that improve compatibility with the tie layer during mechanical recycling. We have investigated the melting temperature depression of single crystals of various polyethylenes embedded in commercial polymeric matrices with various functionalities (ester, acrylate, acetate and methacrylic acid sodium ionomer), which can be potentially used as tie layers. We demonstrate how the concentration and molecular architecture of the matrices affect the melting temperature of the embedded single crystals differently depending on the latter’s molecular architecture. The main finding indicates that the tie layers are more compatible with linear polyethylene than with branched polyethylenes. Indeed, our results show that the heterogeneous Ziegler–Natta linear low-density polyethylene is incompatible with all of the tie layers tested. The depression of melting temperatures observed are in excellent agreement with the results obtained by investigating the rheological behaviour and morphological features of solution-mixed blends in which segmental interactions between polymeric chains have been, in theory, maximized. Because Ziegler–Natta linear density polyethylene is one of the most commonly used polymers as a structural layer in multi-layer applications, the findings of this study are useful as they clearly show the unsuitability of this type of polyethylene for recycling from an eco-design standpoint. The specific molecular requirements for polyethylene layers (branching content less than 0.5/100 carbon atoms) can be specified for use in packaging, guiding the eco-design and valorisation of recycled multi-layered films containing this material.

Effect of the physicochemical properties of SiO2 on performance of supported metallocene catalyst

Effect of the physicochemical properties of SiO2 on performance of supported metallocene catalyst

First example of cationic titanium (III) complexes with crown ether as catalysts for ethylene polymerization

Complex cations with a vacant coordination site are considered as the most plausible catalytically active centers of metallocene and post-metallocene polymerization catalysts. For the first time we demonstrated that cationic titanium (III) complexes stabilized with crown ether can be used as pre-catalysts for ethylene polymerization. In the presence of alkyl aluminum chlorides and MgBu2 as cocatalysts, these complexes catalyze ethylene polymerization to produce Ultra High Molecular Weight Polyethylene (UHMWPE) with productivity up to 4650 kgPE/mol Ti h⋅atm and molecular weight up to 1.8·106 Da. UHMWPE powders were processed by the solid-phase method with subsequent orientation drawing into high-strength (1.4–2.1 GPa) and high-modulus (91–118 GPa) films.

Effects of Spatial Distributions of Active Sites in a Silica-Supported Metallocene Catalyst on Particle Fragmentation and Reaction in Gas-Phase Ethylene Polymerization

Effects of Spatial Distributions of Active Sites in a Silica-Supported Metallocene Catalyst on Particle Fragmentation and Reaction in Gas-Phase Ethylene Polymerization

Amphiphilic olefin block copolymers synthesized by successive coordinative chain transfer and ring-opening polymerizations

Introducing polarity is a necessity for widening the application scope of polyolefins specifically for developing biocompatible products. To this end, we exploit a two-step polymerization process to synthesize poly(ethylene‑b‑caprolactone) PE‑PCL block copolymers, which contain both polar and non-polar segments. First ethylene is polymerized by a generic metallocene catalyst in the presence of ZnEt2 as the chain transfer agent according to the coordinative chain transfer polymerization (CCTP) technique. Terminal zinc atoms are subsequently replaced by hydroxyl groups (PE‑OH) by exposing dormant polymer chains to oxygen. Afterward, ring-opening polymerization (ROP) of ε‑caprolactone is initiated by PE‑OH to form PE‑PCL block copolymers. Successful formation of both blocks is verified by FTIR and NMR spectroscopy. The presence of PCL blocks greatly lowers the crystallinity of ethylene sequences according to XRD and DSC results. Moreover, a second type of PE crystals with more chain folds and lower lamella thickness is found in block copolymers, which is absent in the equivalent physical blend. The diverse crystal structure of block copolymers suggest that phase separation exists between PE and PCL segments. The SEM image of the equivalent physical blend confirms the tendency of PCL and PE chains to phase separate, and infers a compatibilization in the presence of PE‑PCL block copolymers. This phase separation is detected by rheological measurements, as well, where block copolymers show deviations from Maxwell behavior in the terminal relaxation zone at low frequencies. Rheology results also show that the order-disorder transition temperature (TODT) of these block copolymers is higher than 180 °C. These results provide a clear picture from the morphology and utility of such block copolymers specifically for compatibilizing blends of polar polymers and non-polar polyolefins, which significantly broaden the utility of polyolefins.

Surface effect of the MgCl2 support in Ziegler–Natta catalyst for ethylene polymerization: A computational study

Ziegler–Natta (Z–N) catalyst is a remarkable catalyst for olefin polymerization in the petrochemical industry. However, the role of each component remains unclear because of the complicated constituents and structures. MgCl2 is a suitable support for Z–N catalyst, which can improve the activity and stereoselectivity during olefin polymerization and achieve large-scale production of polyolefin under mild conditions. In exploring the role of MgCl2 in the Z–N catalyst system for ethylene polymerization, the stable surface of undercoordinated Mg cations, including (104), (101), (012), (110), and (015) in α-MgCl2 and (010), (011), (012), (110), and (111) in β-MgCl2 was used to load the catalyst, and the mechanism of ethylene polymerization was simulated using the periodic density functional theory. This research found that the curve between the energy barrier of ethylene polymerization and the surface energy of MgCl2 represented the volcano plot, which was consistent with the Sabatier principle. The surface energy of the support was an effective descriptor for predicting catalyst performances.

Effect of a Metallocene Catalyst Mixture on CNT Yield Using the FC-CVD Process

This work studies synthesis of carbon nanotube (CNT) sheet using the high temperature (1400 °C) floating catalyst chemical vapor deposition (FC-CVD) method. Three metallocenes—ferrocene, nickelocene, cobaltocene—and their combinations are used as precursors for metal catalysts in the synthesis process. For the carbon source, an alcohol fuel, a combination of methanol and n-hexane (9:1), is used. First, the metallocenes were dissolved in the alcohol fuel. Then, the fuel mixture was injected into a tube furnace using an ultrasonic atomizer with Ar/H2 carrier gas in a ratio of about 12/1. The synthesis of CNTs from a combination of two or three metallocenes reduces the percentage of metal catalyst impurity in the CNT sheet. However, there is an increase in structural defects in the CNTs when using mixtures of two or three metallocenes as catalysts. Furthermore, the specific electrical conductivity of the CNT sheet was highest when using a mixture of ferrocene and cobaltocene as the catalyst. Overall, the multi-catalyst method described enables tailoring certain properties of the CNT sheet. However, the standard ferrocene catalyst seems most appropriate for large-scale manufacturing at the lowest cost.

Preparation and applications of linear low-density polyethylene

Linear low-density polyethylene (LLDPE) is widely used in many fields like packaging and film due to its chemical resistance and high tensile strength. This review mainly introduces the preparations and applications of LLDPEs produced by Ziegler-Natta catalyst, metallocene-based catalyst, and late transition metal catalyst, respectively. The improved mechanical and conductivity properties of LLDPE by Ziegler-Natta catalysts, higher activity of the metallocene-based catalysts and high performance of LLDPE directly produced by late transition metal were highlighted. The enhancement of the resistance, flexibility, transparency properties, and yield is achieved using those catalysts and mild conditions. This also leads to more applications in electrical, medical, and surgical areas and can reach an industrial scale.

Ultra-high molecular weight polyethylene: preparation and applications

Ultra-high molecular weight polyethylene is a kind of popular engineering material because of its unique properties stemming from high molecular weights. Nowadays, the preparations and applications of this type of material are widely researched. This review mainly focuses on the preparation of ultra-high molecular weight polyethylene using three types of typical catalysts (heterogeneous Ziegler-Natta catalysts, Fujita’s catalysts and α-Diimine Nickel (II) catalysts) and applications in two significant areas (bulletproof membranes and lithium-ion batteries). Ziegler-Natta catalysts and Fujita’s catalysts favor the synthesis of linear ultra-high molecular weight polyethylene, but α-Diimine Nickel (II) catalysis favors β-hydride elimination which leads to branched products. Changes in steric, composition, activators, temperature and pressure will affect the tendency towards different mechanisms and influence structures and properties of final products.

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.

Synthesis of highly spherical Ziegler–Natta catalyst by employing Span 80 as an emulsifier suitable for UHMWPE production

Synthesis of highly spherical Ziegler–Natta catalyst by employing Span 80 as an emulsifier suitable for UHMWPE production