Supported Ziegler-Natta Catalysts Research Articles

MgCl2-Supported Ziegler–Natta Catalysts for Propene Polymerization: Before Activation

MgCl₂-Supported Ziegler–Natta Catalysts for Propene Polymerization: Before Activation

Influence of Cocatalysts on the Performance of Postphthalate Supported Ziegler–Natta Catalysts in Gas-Phase Propylene Polymerization

Influence of Cocatalysts on the Performance of Postphthalate Supported Ziegler–Natta Catalysts in Gas-Phase Propylene Polymerization

Heterogeneity of Active Sites in the Polymer Chain Transfer Reactions at Olefin Polymerization over Multisite Supported Ziegler-Natta Catalysts.

In this review, we summarize and discuss our experimental data published in a number of papers on the transfer reactions of polymer chains in the polymerization of ethylene, propylene, and hexene-1, and the copolymerization of ethylene with α-olefins over multisite supported titanium-magnesium catalysts (TMC). Three groups of transfer reactions are discussed in the review: (1) transfer reactions with AlEt3 cocatalyst, (2) transfer reactions with hydrogen, and (3) transfer reactions with participation of α-olefins in the case of ethylene copolymerization with α-olefins. We have found polymerization conditions where it is possible to observe heterogeneity of active sites of TMC for all three groups of the indicated reactions. It is shown that (1) the transfer reaction with AlEt3 proceeds with higher reactivity on the active sites that produce polymers with low molecular weight; (2) the transfer reaction with hydrogen, in the case of α-olefin polymerization and copolymerization of ethylene with α-olefins, proceeds with higher reactivity on the active sites which produce polymers with high molecular weight; (3) the transfer reaction with α-olefins proceed with higher reactivity on the active sites that produce high molecular weight polymers.

Simulation and optimization of supported Ziegler–Natta catalyst preparation based on AI approach coupled with genetic algorithm

In the present work we are aimed to use powerful and state of the art methodology to optimize catalyst synthesis procedure. In this way, the preparation process of supported Ziegler–Natta catalysts was simulated and optimized through artificial intelligence (AI) methodology coupled with genetic algorithm (GA). The yield of preparation process was investigated through assessing the catalyst activity. The effects of several variables including TiCl4 injection temperature, TiCl4/toluene ratio, and TiCl4 injection time on the activity of prepared catalyst were investigated. In model development, leave-one-out technique was used for training the network. The developed neural network model can be utilized to enhance the efficiency of the catalyst preparation process.

Porous Organic Polymers-Supported Zeigler-Natta Catalysts for Preparing Highly Isotactic Polypropylene with Broad Molecular Weight Distribution.

Porous organic polymers (POPs) have attracted much attention in numerous areas, including catalysis, adsorption and separation. Herein, POP supported Ziegler-Natta catalysts were designed for preparation of isotactic polypropylene (iPP). The POPs-based Ziegler-Natta catalysts exhibited the characteristic of broad molecular weight distribution (MWD > 11) with or without adding an extra internal electron donor. The added internal electron donor 3-methyl-5-tert-butyl-1,2-phenylene dibenzoate (ID-2) used in cat-2 showed good propylene polymerization activity of 15.3 × 106 g·PP/mol·Ti·h, high stereoregularity with 98.2% of isotacticity index and broad molecular weight distribution (MWD) of 12.3. Compared to the MgCl2-supported Ziegler-Natta catalysts (cat-4) with the same ID-2, cat-2 showed higher chain stereoregularity for propylene polymerization. As seen in the TREF results, the elution peak of PP-2 (124.0 °C, 91.7%) is 1.5 °C higher than the isotactic fraction from PP-4 (122.5 °C, 87.2%), and even 1.2 °C higher than PP-5 prepared from ID-3 with the characteristics of high stereoregularity. Moreover, the pentad methyl sequence mmmm of PP-2 (93.0%) from cat-2 is 0.5% higher than that of PP-4 from cat-4. XPS analysis revealed that the minute difference in binding energy of Ti, Mg, C and O atoms exist between the inorganic MgCl2 and the organic polymer based Z-N catalysts. The plausible interaction mechanism of active sites of Mg and Ti with the functional groups in the POP support and the added ID was proposed, which could be explained by their high stereoregularity and the broad molecular weight distribution of the POP-based Z-N catalysts.

Impact of Process Poisons on the Performance of Post‐Phthalate Supported Ziegler–Natta Catalysts in Gas Phase Propylene Polymerization

AbstractThe impact of common process catalyst poisons on the performance of a 6th generation Ziegler–Natta catalysts during the gas phase polymerization of propylene are examined using two approaches: introducing propylene without purification, or with one or two sets of purification columns, and by introducing carbon dioxide (CO2), oxygen (O2), water (H2O), methanol (CH3OH), ethyl acetate (C4H8O2) and dimethyl sulfoxide (C2H6SO) during the polymerization. As expected, purification columns increases the catalyst activity significantly, slightly reduce catalyst decay. Injecting TiBA during the reaction leads to an activity increase. The addition of two full sets of columns substantially increased the repeatability of polymerization reactions. The power of deactivation of poisons injected during the polymerization reaction is: O2 > CO2 > CH3OH > C2H6SO > C4H8O2 > H2O. Adding CO2, O2, and CH3OH resulted in a progressive decrease in molecular weight while almost no effect is observed with H2O. However, C4H8O2, and C2H6SO resulted in a mild increase in molecular weight. Additionally, the effects on crystallinity and stereoregularity are similar where CO2, O2, H2O and CH3OH caused a progressive decrease while C4H8O2 and C2H6SO resulted in a mild increase, indicating some isotacticity control by these two poisons.

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.

The atomic defects on the (104) and (110) surfaces of the MgCl2-supported Ziegler–Natta catalyst: a periodic DFT study

This work presents a DFT study on the effects of atomic defects in the MgCl2-supported Ziegler–Natta catalyst. The adsorption behaviours of TiCl4 and internal donors on the ideal and defective MgCl2(104) and (110) surfaces were investigated.

Molecular-level insights into adsorption of a novel silyl ester donor on essential MgCl2 facets of supported Ziegler–Natta catalysts

This article deals with the adsorption properties of a new silyl ester donor called bis(benzoyloxy)dimethylsilane (BDMS) on the MgCl2 support of the Ziegler–Natta catalysts in both conventional and zip modes of coordination. The results confirmed the strong (by up to 47.6 kcal/mol at PBEh/TZVP) preference of BDMS for bridging over chelating or monodentate binding modes on both tetracoordinate and pentacoordinate Mg atoms. Among the spontaneous events, the lowest but appreciable preference was predicted for monodentate chemisorption on penta-coordinated Mg. The zero-point energy (ZPE) values confirmed that BDMS could be adsorbed more strongly, by 7.0 kcal/mol, on the (110) facet than on the (104) surface of the MgCl2 matrix. The enthalpy changes confirmed the ability of BDMS to effectively stabilize the lateral crystallite terminations. The observed characteristics were explained in terms of the quantum theory of atoms in molecules, natural bond orbital population, reduced density gradient, non-covalent interactions, and charge density difference. While some in-plane redistribution of charges was demonstrated, the electron transfer did not exceed 0.1 e. Overall, BDMS was shown to be more selective than the commonly used phthalate donors.

Responses of a Supported Ziegler–Natta Catalyst to Comonomer Feed Ratios in Ethylene–Propylene Copolymerization: Differentiation of Active Centers with Different Catalytic Features

Ethylene–propylene (E/P) copolymerization with a TiCl4/Di/MgCl2–TEA/De (Di, internal donor; De, external donor; TEA, triethylaluminum)-type Ziegler–Natta catalyst was conducted at various comonomer...

Gas phase polymerization of ethylene towards UHMWPE.

For the first time, ultra-high molecular weight polyethylene (UHMWPE) was produced in gas phase process with a new fluidized bed concept where the solids are dispersed phase and the gas is bulk phase as opposed to conventional fluidized bed reactors (FBRs). With this concept, UHMWPE with average molecular weights about 1-6,9 × 106 g mole-1 were produced with a commercial supported Ziegler-Natta catalyst by using a gas phase mini semibatch reactor system. Additionally, optimum conditions of gas phase polymerization for the best results of productivity, catalyst activity, molecular weight and crystallinity were determined by Taguchi experimental design and catalyst stability at the optimum condition was tested by video microscopy polymerization. The characterization of products was carried out experimentally by TGA, DSC, FTIR, and NMR.

Direct Preparation of Transparent Isotactic Polypropylene with Supported Ziegler–Natta Catalysts Containing Novel Eco-friendly Internal Electron Donors

This study reported novel eco-friendly Ziegler-Natta catalysts containing bio-derived maleic rosinate tri-n-butyl and maleic rosinate tri-n-octyl as internal electron donors for propylene polymeriz...

Determination and tracing of active and dormant propagation chains in 1-hexene polymerization with supported Ziegler-Natta catalyst

Propagation chains with 1,2 and 2,1 last-inserted monomer unit in 1-hexene polymerization with MgCl2-supported Ziegler-Natta catalysts were quench-labeled by thiophene-2-carbonyl chloride, and the two kinds of 2-thenoyl-labeled chain ends were determined by 1H NMR analysis. The number of labeled chains was noticeably smaller than the number of dead chains formed by chain transfer with alkylaluminum cocatalyst, and grew with time more slowly than the latter, showing that side reactions between the quencher and Al-polymeryl moieties are negligible. The active sites with 2,1 last-inserted monomer were halted in dormant state, which lead to their gradual accumulation in the 30 s polymerization process. The catalyst containing phthalate type internal donor has higher percentage of dormant sites as compared with the catalyst containing diol ester. The combination of acyl chloride quench-labeling and 1H NMR analysis forms a reliable and easily accessible method of tracing and characterizing active sites in transition metal catalyzed olefin polymerization.

Towards the design of a mixture of diether and succinate as an internal donor in a MgCl2-supported Ziegler–Natta catalyst

An investigation into competitions of mixtures of internal donors for interaction with MgCl2was carried out and the subsequent influence on catalyst performance was studied.

Effect of Catalyst Type on the Copolymerization of Styrene/1-Hexene and Exploring of Their Structural and Thermal Properties

The effect of catalyst type on styrene/1-hexene copolymerization reactions was investigated. The copolymerization reactions were performed using conventional free radical polymerization, atom transfer radical polymerization (ATRP) and Ziegler-Natta polymerization methods. Copolymers containing different 1-hexene compositions were synthesized and characterized by 1H NMR, GPC and DSC methods. The monomer reactivity ratios for free radical copolymerization were calculated using linear methods and found to be r1 ~ 25 and r2 → 0 for styrene and 1-hexene, respectively. The increases of 1-hexene mole fraction in ATRP synthesized copolymers showed that CuCl/L promotes 1-hexene cross propagation significantly. Furthermore, 1-hexene cannot participate in self-propagation reaction. In the polymerization assisted by supported Ziegler-Natta catalyst, the conversion of the reaction was increased with mole fraction of 1-hexene in the feed, which indicated the higher reactivity of this monomer. Finally, the thermal properties of copolymers were studied by DSC.

SiO2‐covered graphene oxide nanohybrids for in situ preparation of UHMWPE/GO(SiO2) nanocomposites with superior mechanical and tribological properties

ABSTRACTThe modified Hummer technique was used in the preparation of graphene oxide (GO) nanosheets, and then SiO2 decorated GO [GO(SiO2)] nanosheets were synthesized via the sol–gel method. Then, ultrahigh‐molecular‐weight polyethylene (UHMWPE) nanocomposites loaded with 0.5, 1, 1.5, and 2 wt % of GO(SiO2) were prepared using magnesium ethoxide/GO(SiO2)‐supported Ziegler–Natta catalysts via the in situ polymerization. Morphological study of the prepared polymer powders was assessed using field‐emission scanning electron microscopy, which showed that GO(SiO2) nanohybrids have been uniformly dispersed and distributed into the UHMWPE matrix. Also, the neat UHMWPE and its nanocomposites were evaluated with different analyses, including viscosity‐average molecular weight measurement, differential scanning calorimetry, thermogravimetric analysis, tensile test, scratch hardness, and pin‐on‐disk test. The characterization of the UHMWPE nanocomposites indicated that many characterizations, including the mechanical, thermal, and tribological properties of UHMWPE, were significantly improved by incorporation of these new nanosheets in spite of the molecular weight reduction of the polymeric matrix and the improved flowability and processability of the produced nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47796.

Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler⁻Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae.

The kinetic behaviors of ethylene and propylene polymerizations with the same MgCl2-supported Ziegler–Natta (Z–N) catalyst containing an internal electron donor were compared. Changes of polymerization activity and active center concentration ([C*]) with time in the first 10 min were determined. Activity of ethylene polymerization was only 25% of that of propylene, and the polymerization rate (Rp) quickly decayed with time (tp) in the former system, in contrast to stable Rp in the latter. The ethylene system showed a very low [C*]/[Ti] ratio (<0.6%), in contrast to a much higher [C*]/[Ti] ratio (1.5%–4.9%) in propylene polymerization. The two systems showed noticeably different morphologies of the nascent polymer/catalyst particles, with the PP/catalyst particles being more compact and homogeneous than the PE/catalyst particles. The different kinetic behaviors of the two systems were explained by faster and more sufficient catalyst fragmentation in propylene polymerization than the ethylene system. The smaller lamellar thickness (<20 nm) in nascent polypropylene compared with the size of nanopores (15–25 nm) in the catalyst was considered the key factor for efficient catalyst fragmentation in propylene polymerization, as the PP lamellae may grow inside the nanopores and break up the catalyst particles.

Mechanistic study on comonomer effect in ethylene/1-hexene copolymerization with TiCl4/MgCl2 model Ziegler-Natta catalysts

Two MgCl2-supported Ziegler-Natta model catalysts were prepared by contacting activated MgCl2 with deficient or excess amount of TiCl4. Ethylene/1-hexene copolymerization with the catalysts was conducted under different 1-hexene feed, and active center concentration of the reaction system was determined by quench-labeling method using thiophene-2-carbonyl chloride as the quencher. The catalytic activity was only moderately enhanced (increment <50%) by adding 1-hexene in ethylene polymerization with the model catalyst (Cat-1) of 0.1 wt% Ti content, and the active center ratio ([C*]/[Ti]) was only slightly increased (from 64 to 72 mol%). The comonomer activation effect in Cat-1 catalyzed copolymerization was mainly attributed to increase of apparent propagation rate constant by the comonomer, which can be explained by reduction of mass transfer barrier in the polymer/catalyst particles because of larger monomer diffusion coefficients in the copolymer phase than in the more crystalline polyethylene phase. In contrast, the activity was nearly tripled by adding 1-hexene when the catalyst of 1.47% Ti content (Cat-2) was used, meanwhile its [C*]/[Ti] was also tripled (from 15 to 49 mol%). The strong comonomer activation effect in Cat-2 catalyzed copolymerization was caused by marked increase of active center concentration. In this case, fragmentation of the polymer/catalyst particles was intensified by adding the comonomer, and more active centers that were originally inaccessible to the cocatalyst and monomer were exposed through the particle fragmentation. According to the results of this work, the comonomer effect in conventional supported Ziegler-Natta catalysts can be explained by the combination of physical factor (increase in diffusion coefficient) and chemical factor (exposure of inaccessible active center precursors through particle fragmentation).

Synthesis of Perylene-Tagged Internal and External Electron Donors for Magnesium Dichloride Supported Ziegler–Natta Catalysts

We report on the synthesis of three perylene-tagged electron donors representing three major types – phthalates, diethers, and alkoxysilanes – which are of importance for the subsequent studies of MgCl2-supported Ziegler–Natta catalysts by means of laser scanning confocal fluorescence microscopy. The obtained products were unambiguously characterized, including by X-ray crystal structure analysis; their photophysical properties (absorption and emission spectra) were investigated as well. Additionally, a reliable and convenient protocol for the multigram synthesis of the required starting material – 3-bromo­perylene (PerBr) – was developed. The key step of this method was synthesis of trialkylsilyl-substituted perylenes, which were further separated by means of flash chromatography followed by conversion of the isolated 3-trialkylsilyl-substituted product to PerBr.

Trans‐1,4‐stereospecific copolymerization of ethylene and isoprene catalyzed by MgCl2‐supported Ziegler–Natta catalyst

ABSTRACTCopolymerization of ethylene and isoprene (Ip) catalyzed by TiCl4/MgCl2‐Al(i‐C4H9)3 catalyst was systematically studied. Homopolymer of ethylene and Ip were synthesized under the same conditions for making comparisons. Proton nuclear magnetic resonance was employed to characterize chain structure of the copolymer. Influences of Ip concentration, molar ratio of cocatalyst to Ti and reaction temperature on the copolymerization activity and copolymer chain structure were investigated. The copolymerization activity was evidently lowered by increasing Ip concentration, and the Ip content in copolymer was rather low under reaction conditions leading to higher activity. Insertions of Ip in polymer chain showed rather high regioselectivity for 1,4‐connections (&gt;85%) and medium to high stereoselectivity for trans‐1,4‐isomer (&gt;70%) under typical conditions, but the regio and stereoselectivities tended to decrease with decrease in Ip concentration and increase in Al/Ti ratio. Melting temperature of the copolymer decreased with increase of Ip content, indicating incorporation of Ip units in most of the copolymer chains. This work has proved feasibility of introducing small amount of Ip units with high trans‐1,4‐stereoselectivity into ethylene/isoprene copolymer chains by catalyzed copolymerization with MgCl2‐supported Ziegler–Natta catalysts. The copolymer is expected to be a promising candidate of easily degradable film or packaging materials. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2715–2722