Activity For Ethylene Polymerization Research Articles

Structure-performance relationship of Mg(OEt)2-based Ziegler-Natta catalysts

A multivariate aspect has hampered the clarification of structure-performance relationships in heterogeneous Ziegler-Natta olefin polymerization catalysis. Here, 16 catalyst samples were prepared using Mg(OEt)2 support precursors with different particle architectures. They were fingerprinted based on a series of characterization and analytical methods. In a pairwise correlation analysis, none of structural features (such as particle size and pore volume) exhibited a clear correlation with ethylene polymerization performance. However, compound features created among different structural features reasonably reproduced the ethylene polymerization activity as well as 1-hexene incorporation efficiency, where a negative influence of pores with the size below 10 nm was dictated.

O‐Trityl phenoxy‐imino vanadium (III) complexes: synthesis, characterization, and catalysis on ethylene (co)polymerization

Several phenoxy‐imine ligands bearing o‐trityl group in phenoxy moiety RN=CHArOH (Ar = C6H2(CPh3)tBu, R = 2,6‐Me2C6H3 (L1H); 2,6‐iPr2C6H3 (L2H); 3,5‐(CF3)2C6H3 (L3H); 3,5‐(OMe)2C6H3 (L4H); CHPh2 (L5H); CPh3 (L6H)) were synthesized and characterized by1H NMR and 13C NMR spectroscopy. The vanadium complexes based on these ligands LVCl2(THF)2 (1–6) were synthesized via conventional transmetalation reaction in moderate to high yields. Complexes 1–6 were fully characterized by FT‐IR, elemental analyses and the molecular structures of 1, 2·H2O, (2·H2O)2(μ‐Cl)2, 4, and 5 were confirmed by X‐ray crystallographic analysis in which the six‐coordinated vanadium centers are in a typical octahedral geometry. Upon activation with Et2AlCl in toluene, complexes 1–6 showed high activities in ethylene polymerization affording polymers with moderate molecular weight (5.9–11.8 × 104 Da). Moreover, in hexane or CH2Cl2, 1–6/Et2AlCl exhibited enhanced activities. When activated with MAO or MMAO in toluene, these complexes showed relatively low activities but afforded polymers with ultra‐high molecular weight (up to 3.30 × 106 Da). 1–6/Et2AlCl also showed high activities in ethylene/1‐hexene copolymerization at room temperature giving moderate molecular‐weight polymers (6.5–11.4 × 104 Da) with co‐monomer incorporation being of 6.0 ~ 7.8%.

Binuclear titanium complexes coordinated by rigid p‐phenylene linked bis‐β‐carbonylenamine: Synthesis, structure, ethylene polymerization and copolymerization with 1,5‐hexadiene

Binuclear complexes for olefin polymerization have attracted great attention due to their unique catalytic properties compared with their mononuclear counterparts. Here a series of p‐phenylene‐bridgedbis‐β‐carbonylenamine ligands and their binuclear Ti complexes Ti2L1–Ti2L3 were prepared and characterized by 1H NMR, 13C NMR, Fourier transform infrared spectroscopy, and elemental analysis. The binuclear complex Ti2L3 bearing an octylthio sidearm was further investigated by single‐crystalX‐ray diffraction, which revealed that the ligand was of β‐imino enol form, with one titanium atom ligated with six other atoms, forming a deformed octahedral configuration. Furthermore, the ligand in Ti2L3 adopted a cis configuration, which was different from the trans configuration of its m‐phenylene‐bridged derivatives. These binuclear complexes (Ti2L1–Ti2L3) could catalyze ethylene polymerization and copolymerization with 1,5‐hexadiene(1,5‐HD) efficiently under modified methylaluminoxane activation. Compared with the mononuclear complex TiL5, the binuclear catalysts were thermally more stable and showed higher activity for ethylene polymerization at higher temperatures. The activity of these titanium complexes for the copolymerization of ethylene with 1,5‐HD were over 106 g/mol Ti.h.atm, almost twice as high as for homopolymerization. Compared with the mononuclear analogue TiL5 and the m‐substituted binuclear derivative Ti2L4, binuclear catalyst Ti2L2 showed higher activity and insertion rate of the comonomer. The activity of Ti2L2 was two to three times higher than that of TiL5 and Ti2L4, indicating that p‐substituted binuclear catalysts generate clear bimetallic synergistic effect for the copolymerization of ethylene and 1,5‐HD. Meanwhile, 1,5‐HD takes 1,3‐cyclopentyl form in the polymer by 1,3‐insertion. The copolymer prepared by binuclear catalysts had higher molecular weight and wider molecular weight distribution than that prepared by the mononuclear catalyst.

Study of supported catalysts, prepared via binding of Fe(II) bis(imino)pyridyl complex with silica, modified by alumina: Effect of surface Lewis acidic sites on catalyst composition and activity in ethylene polymerization

In this work we present the data on the formation and composition of new supported catalysts for ethylene polymerization, prepared by interaction of Fe(II) bis(imino)pyridyl complex (LFeCl2) with silica, modified by introduction of alumina compounds (SiO2(nAl)) for generation of Lewis acidic sites (LAS) on the silica surface. Data on the content of LAS with different acidity in SiO2(nAl) supports and on the interaction of LFeCl2 with these sites were obtained. It was found that interaction of LFeCl2 with the most acidic sites of SiO2(nAl) supports leads to formation of the most active catalysts for the ethylene polymerization.

Enhancing performance of α‐diiminonickel precatalyst for ethylene polymerization by substitution with the 2,4‐bis(4,4'‐dimethoxybenzhydryl)‐6‐methylphenyl group

High activities in ethylene polymerization predetermine α‐diiminonickel precatalysts for potential industrial applications. In our study, we have synthesized and characterized a series of unsymmetrical 1‐(2,4‐bis(4,4′‐dimethoxybenzhydryl)‐6‐MeC6H2N)‐2‐arylimino‐acenaphthylene nickel(II) halides. The single‐crystal X‐ray diffraction study of representative compounds reveals distorted tetrahedral geometry. On activation with either Me2AlCl or modified methylaluminoxane, these nickel complexes exhibit high activities of the order of 106 g of PE (mol of Ni)−1 h−1 and produce polyethylene of generic application characterized by high molecular weight, narrow molecular weight distribution, and moderate degree of branching. The substituents at the ligands affect the catalytic performance of the nickel complexes and tune the microstructure of the resultant polyethylene.

A comprehensive study on highly active pentiptycenyl-substituted bis(imino)pyridyl iron(II) mediated ethylene polymerization

Ligand steric bulk is of paramount importance in late transition-metal mediated olefin polymerization. In this contribution, we designed and prepared two structurally similar bis(imino)pyridyl iron(II) complexes bearing 2,6-bis(dibenzhydryl)phenyl N-aryl moiety (Ph-Fe) and pentiptycenyl N-aryl moiety (Ipty-Fe) to reveal the huge effect of steric bulk on ethylene polymerization. Two iron(II) complexes were confirmed by NMR spectroscopy, mass spectroscopy, elemental analysis, and vital X-ray diffraction analysis, which indicates that Ph-Fe has a larger buried volume around the metal center than Ipty-Fe (%Vbur: 55.5 vs. 52.7). As a result, in the presence of Al reagent, Ph-Fe showed extremely low activity for ethylene polymerization, but Ipty-Fe with a less steric blockage exhibited much higher (two orders of magnitude) activity (up to 25,500 kg mol−1 h−1). Reaction temperature, time, pressure, type and amount of Al reagents were comprehensively studied to evaluate and compare these two iron(II) complexes. More interestingly, chain-end-functionalization of these obtained polyethylenes bearing vinylic end-groups could be achieved in situ by the Friedel-Crafts addition to aromatic toluene as the reaction solvent at elevated temperature or high ratio of [Al]/[Fe].

A Titanium(IV) Complex with an OSO-Type Ligand as a Catalyst for the Synthesis of Ultrahigh-Molecular-Weight Polyethylene

Coordination compounds of titanium(IV) with OSO-type ligands have been prepared and characterized, and their catalytic activity in ethylene polymerization has been studied. It has been shown that in the presence of an {Et2AlCl + Bu2Mg} binary cocatalyst, the activity of the titanium-containing catalyst system reaches 1629 kgPE mol(Ti)−1 h−1 and leads to the preparation of ultrahigh-molecular-weight polyethylene (UHMWPE). The UHMWPE reactor powder has been processed by a solvent-free method to high-strength and high-modulus films (σ = 2.32 GPa, E = 125 GPa).

Mathematical modeling of ethylene polymerization over advanced multisite catalysts: an artificial intelligence approach

Recent developments in multisite catalysts based on metallocenes and post-metallocenes attracted the attention of researchers and industrial petrochemical companies due to the production of high-performance polymeric materials which generally are not achievable based on Ziegler–Natta catalysts. In this study, with the aim of predicting the average molecular weight of produced polyethylene and activity of ethylene polymerization using multisite catalysts, robust precise models based on artificial neural networks are developed. The average error for the prediction of the average molecular weight and activity are 3.76% and 5.89%, respectively. The Leverage method was used to check the reliability of the proposed model and the quality of experimental data which have been used for model development. The results showed that just a few data points are outside of the applicability domain of the developed models, confirming that both developed models and their predictions are statistically correct. Comparison of the artificial neural network models with other artificial intelligence approaches including support vector machine and group method of data handling type neural networks illustrates the better performance and robustness of the proposed models. The results of this study promise that neural networks can be used as reliable models with reasonable accuracy to estimate the performance of ethylene polymerization over this type of new metallocene/post-metallocene multisite catalysts.

Получение композиционных материалов на основе полиэтилена методом полимеризации in situ на титан-магниевом катализаторе, закрепленном на поверхности углеродных нанотрубок различного типа

The data on the preparation of composite materials containing polyethylene and multi-walled carbon nanotubes (MWCNTs) of the Taunit brand are presented. To obtain these composites by in situ polymerization, a catalytic system formed by the interaction of an organomagnesium compound and TiCl4 on the surface of nanotubes was used. The catalyst fixed on the MWCNT surface has a high activity in ethylene polymerization and allows to obtain a polymer with different molecular weight. The data on the formation of a polymer on the MWCNT surface and the morphology of composites formed on various Taunit samples are presented.

α-Diimine nickel complexes bearing axially bulky terphenyl and equatorially bulky dibenzobarrelene groups: synthesis, characterization and olefin polymerization studies

A new family of asymmetric α-diimine nickel complexes bearing axially and equatorially bulky groups were synthesized successfully. They exhibited high catalytic activities for ethylene polymerization and afforded ultra-high-molecular-weight elastomeric polyethylenes.

High molecular weight polyethylenes of narrow dispersity promoted using bis(arylimino)cyclohepta[b]pyridine-cobalt catalysts ortho-substituted with benzhydryl & cycloalkyl groups.

A one-pot template strategy has been utilized to synthesize sterically enhanced bis(imino)cyclohepta[b]pyridine-cobalt(ii) chlorides, [2-{(Ar)N[double bond, length as m-dash]CMe}-9-{N(Ar)}C10H10N]CoCl2 (Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2Co1, 2-(C6H11)-4,6-(CHPh2)2C6H2Co2, 2-(C8H15)-4,6-(CHPh2)2C6H2Co3, 2-(C12H23)-4,6-(CHPh2)2C6H2Co4, 2,6-(C5H9)2-4-(CHPh2)C6H2Co5). All five complexes have been characterized by a combination of FT-IR spectroscopy, elemental analysis and single crystal X-ray diffraction. The molecular structures of Co1, Co3 and Co5 highlight the substantial steric hindrance imparted by the 2-cycloalkyl-6-benzhydryl or 2,6-dicyclopentyl ortho-substitution pattern; distorted square pyramidal geometries are exhibited in each case. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the complexes (apart from Co4/MAO) were active ethylene polymerization catalysts (up to 3.70 × 106 g PE per mol (Co) per h for Co5/MMAO), operating effectively at temperatures between 50 °C and 60 °C, producing polyethylenes with high molecular weights (up to 589.5 kg mol-1 for Co3/MAO). Furthermore, all polymers were highly linear (Tm > 130 °C) with narrow dispersities (Mw/Mn range: 2.0-3.0). The coexistence of two chain termination pathways, β-H elimination and transfer to aluminum, has been demonstrated using 13C/1H NMR spectroscopy.

Ethylene Polymerization and Copolymerization with Polar Monomers by Benzothiophene-bridged BPMO-Pd Catalysts

A series of new bisphosphine-monoxide (BPMO) ligands based on benzothiophene backbone and the corresponding palladium complexes {K2-2-P(O)(Ph)2-3-PR1R2-C8H4S}PdMeCl {2a: R1 = R2 = Ph; 2b: R1 = R2 = 2-OMe-Ph; 2c: R1 = R2 = 2-CF3-Ph; 2d: R1 = Ph, R2 = 2-(2′,6′-(OMe)2C6H3)-C6H4} were synthesized and fully characterized by 1 H-, 13C-, 31P-, and 2D-NMR spectroscopy and single-crystal X-ray diffraction. In the presence of Na+B[3,5-(CF3)2C6H3]4− (NaBArF), these complexes showed very high activities (up to 2.0 × 107 gmo−1·h−1) for ethylene polymerization. More significantly, these catalysts enabled the copolymerization of ethylene with a broad scope of commercially available polar comonomers such as acrylates, acrylic acid, acrylonitrile, vinyltrialkoxysilane, allyl acetate, and long-chain 6-chloro-1-hexene to give functionalized polyethylene with reasonable catalytic activities (up to 106 g·mol−1·h−1) and incorporations (up to 5.3 mol%). This contribution suggests that, besides the modulation of conventionally steric and electronic factors, the connectivity (at different linking positions) of BPMO (P,O) donors to the heteroaryl backbone also greatly influences the catalyst properties in terms of catalytic activity, polymer branching content, comonomer scope, and comonomer incorporation.

Early Metal Di(pyridyl) Pyrrolide Complexes with Second Coordination Sphere Arene-π Interactions: Ligand Binding and Ethylene Polymerization.

Early metal complexes supported by hemilabile, monoanionic di(pyridyl) pyrrolide ligands substituted with mesityl and anthracenyl groups were synthesized to probe the possibility of second coordination sphere arene−π interactions with ligands with potential for allosteric control in coordination chemistry, substrate activation, and olefin polymerization. Yttrium alkyl, indolide, and amide complexes were prepared and structurally characterized; close contacts between the anthracenyl substituents and Y-bound ligands are observed in the solid state. Titanium, zirconium, and hafnium tris(dimethylamido) complexes were synthesized, and their ethylene polymerization activity was tested. In the solid state structure of one of the Ti tris(dimethylamido) complexes, coordination of Ti to only one of the pyridine donors is observed pointing to the hemilabile character of the di(pyridyl) pyrrolide ligands.

Activity Enhancement of MgCl2-supported Ziegler-Natta Catalysts by Lewis-acid Pre-treatment for Ethylene Polymerization

Ziegler-Natta precatalysts were synthetized from Lewis-base-modified-MgCl2 supports and treated by various Lewis acids, prior to activation by triethylaluminum, in order to increase their activity in ethylene polymerization. BCl3 provided the highest increase in activity. Interestingly, polymerization results showed no substantial modification of polymer properties, which is consistent with that Lewis acid only promotes the creation of new active sites, after activation by TEA, possessing very similar features to the original ones achievable with conventional precatalysts (i.e. without Lewis-acid treatment).

Nickel Catalysts Activated by rGO Modified with a Boron Lewis Acid To Produce rGO-Hyperbranched PE Nanocomposites

The synthesis, characterization, and ethylene reactivity of a nickel-activated α-cyano-β-ketoiminate complex with B(C6F5)3 is reported. The X-ray diffraction studies of the Ni complex 1 revealed that a weak interaction between the distal aryl rings of the N-terphenyl moiety could be responsible for the low molecular weights and highly branched microstructure of the polyethylene compounds. In addition, a supported single-site Lewis acid based on reduced graphene oxide, rGO-O-B(C6F5)2, was used, and we studied its ability to activate complex 1 for the generation of polyethylene/reduced graphene oxide nanocomposites. The supported catalyst rGO-B(C6F5)2-NiCN exhibited an ethylene polymerization activity that was approximately 2 times greater than that of the unsupported system. Meanwhile, the microstructure of the polyethylene nanocomposites was analyzed by 13C NMR, revealing the presence of a low molecular weight and hyperbranched motif due to the presence of sec-butyl groups. These results indicated that the graphene support actively participated in the polymerization process. The morphological examinations of the nanocomposites by TEM revealed the effective exfoliation and good dispersion of rGO in the polymer matrix at the nanoscale level.

Exceptionally high molecular weight linear polyethylene by using N,N,N′‐Co catalysts appended with a N′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group

The bis(arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC6H4)2CH}2–4‐NO2}]‐6‐(CMeNAr)C5H3N (Ar = 2,6‐Me2C6H3 L1, 2,6‐Et2C6H3 L2, 2,6‐i‐Pr2C6H3 L3, 2,4,6‐Me3C6H2 L4, 2,6‐Et2–4‐MeC6H2 L5), each containing one N′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group, have been synthesized by two successive condensation reactions from 2,6‐diacetylpyridine. Their subsequent treatment with anhydrous cobalt (II) chloride gave the corresponding N,N,N′‐CoCl2 chelates, Co1 – Co5, in excellent yield. All five complexes have been characterized by 1H/19F NMR and IR spectroscopy as well as by elemental analysis. In addition, the molecular structures of Co1 and Co3 have been determined and help to emphasize the differences in steric properties imposed by the inequivalent N‐aryl groups; distorted square pyramidal geometries are adopted by each complex. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), precatalyts Co1 – Co5 collectively exhibited very high activities for ethylene polymerization with 2,6‐dimethyl‐substituted Co1 the most active (up to 1.1 × 107 g (PE) mol−1 (Co) h−1); the MAO systems were generally more productive. Linear polyethylenes of exceptionally high molecular weight (Mw up to 1.3 × 106 g mol−1) were obtained in all cases with the range in dispersities exhibited using MAO as co‐catalyst noticeably narrower than with MMAO [Mw/Mn: 3.55–4.77 (Co1 – Co5/MAO) vs. 2.85–12.85 (Co1 – Co5/MMAO)]. Significantly, the molecular weights of the polymers generated using this class of cobalt catalyst are higher than any literature values reported to date using related N,N,N‐bis (arylimino)pyridine‐cobalt catalysts.

Heteroaryl Backbone Strategy in Bisphosphine Monoxide Palladium-Catalyzed Ethylene Polymerization and Copolymerization with Polar Monomers

The backbone structure of ligand is of critical importance to modulate the selectivity and the reactivity of catalyst. In this contribution, heteroaryl backbone (benzo)thiophene was for the first time installed on bisphosphine-monoxide (PO) ligands. Corresponding palladium complexes {κ2-2-P(2-OMe-Ph)2-3-P(O)(Ph)2-4–Br-C4HS}PdMeCl (2a) and {κ2-2-PR1R2-3-P(O)(Ph)2-C8H4S}PdMeCl {2b: R1 = R2 = 2-OMe-Ph; 2c: R1 = R2 = Cy; 2d: R1 = Ph, R2 = 2-(2′,6′-(OMe)2C6H3)-C6H4} and the compared phenylene-linked palladium complex {κ2-1-P(2-OMe-Ph)2-2-P(O)(Ph)2-C6H4}PdMeCl (2e) were synthesized and fully characterized by 1H, 13C, 31P, and 2D-NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction (2a, 2b, and 2d). In the presence of Na+B[3,5-(CF3)2C6H3]4– (NaBArF4), these complexes showed high activities (up to 10 000 kg mol–1 h–1) for ethylene polymerization that are comparable to the prototype phenylene-linked BPMO-Pd catalysts, producing moderate to high molecular weight (Mn up to 90 kDa) linear polyet...

A New Class of Pyridine-Amide Containing Ti and Zr Based Catalysts for Olefin Polymerization: Influence of Ligand Substituents

Two tridendate pyridine-amide ligands in di-deprotonated form have been used to synthesize new titanium and zirconium complexes. The molecular structure of pentafluoro containing Titanium and Zirconium complexes were determined by DFT calculations. These new metal complexes have been further evaluated for ethylene polymerization activity in the presence of co-catalyst methylaluminoxane (MAO) under atmospheric pressure, producing polyethylenes with moderate molecular weights and unimodal molecular weight distribution. Remarkably, zirconium complexes show higher activity than titanium complexes under the same polymerization condition. The catalytic activity of all the complexes were found to be temperature dependent and reach their highest efficiency at 70 °C. The influence of the nature of the ligands and reaction parameters upon the catalytic activities has been studied. Additionally, the pentafluoro containing Zirconium and Titanium complexes were further evaluated for the copolymerization of ethylene and propylene and exhibited good catalytic activity. A new class of titanium and zirconium based metal complexes were synthesised from pyridine-amide containing ligands. The synthesised complexes have been evaluated for ethylene polymerization in the presence of co-catalyst methylaluminoxane (MAO) under atmospheric pressure. Interestingly, zirconium complexes show high catalytic activities than titanium complexes under the same polymerization condition.

Formation of Ziegler‐type catalytic systems on the surface of multi‐walled carbon nanotubes for the production of composite materials by in situ polymerization

ABSTRACTThe peculiarity of formation of Ziegler‐type catalytic systems prepared using organoaluminum (AlR3) and organomagnesium (MgR2) on the surface of multi‐walled carbon nanotubes (MWCNTs) was revealed. We have found first AlR3 and MgR2 interact with different sites on MWCNT surface. It was demonstrated by IR spectroscopy that organoaluminum compounds were immobilized on the hydroxyl‐containing groups on MWCNT surface. Organomagnesium compounds were immobilized on the topological structural defects of MWCNTs; hydroxyl‐containing groups were not required for their immobilization. Further interaction between TiCl4 and organomagnesium compound immobilized on the MWCNT surface yielded a catalyst containing titanium and magnesium chlorides (an analogue of the known titanium–magnesium catalysts), which exhibits an enhanced activity in ethylene polymerization. The effect of polymerization conditions on molecular weight characteristics of polyethylene in the MWCNT/PE composite material produced by in situ polymerization over the catalyst immobilized on the MWCNT surface was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48212.

Activity and Thermal Stability of Cobalt(II)-Based Olefin Polymerization Catalysts Adorned with Sterically Hindered Dibenzocycloheptyl Groups.

Five examples of unsymmetrical 2-(2,4-bis(dibenzocycloheptyl)-6-methylphenyl- imino)ethyl)-6-(1-(arylyimino)ethyl)pyridine derivatives (aryl = 2,6-Me2C6H3 in L1; 2,6-Et2C6H3 in L2; 2,6-i-Pr2C6H3 in L3; 2,4,6-Me3C6H2 in L4 and 2,6-Et2-4-MeC6H2 in L5) were prepared and characterized. Treatment with CoCl2 offered the corresponding cobalt precatalysts Co1–Co5, which were characterized by FT-IR and NMR spectroscopy as well as elemental analysis. The molecular structures of Co3 and Co4 determined by single crystal X-ray diffraction revealed distorted square pyramidal geometries with τ5 values of 0.052–0.215. Activated with either MAO or MMAO, the precatalysts displayed high activities in ethylene polymerization, where Co1 with the least bulky substituents exhibited a peak activity of 1.00 × 107 g PE mol−1 (Co) h−1 at 60 °C. With MAO as a cocatalyst, the activity was reduced only by one order of magnitude at 90 °C, which implies thermally stable active sites. The polymerization product was highly linear polyethylene with vinyl end groups. Co3 with the most sterically hindered active sites was capable of generating polyethylene of high molecular weight, reaching 6.46 × 105 g mol−1. Furthermore, high melting point and unimodal molecular weight distribution were observed in the resulting polyethylene. It must be stressed that the thermal stability of the catalyst and the molecular weight of the obtained polyethylene attain the highest values reported for the unsymmetrical 2,6-bis(imino)pyridylcobalt (II) chloride precatalysts.