Novel catalyst systems based on Ni(II), Ti(IV), and Cr(III) complexes for oligo-and polymerization of ethylene (original) (raw)
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Distinct new catalysts for utilization of ethylene gas to polymer and oligomer
Applied Petrochemical Research, 2013
Bi-nickel-center catalysts were prepared by Schiff-base condensation of 2,3-butanedione with 2,6-diisopropylaniline; 2-5-butylaniline, 2-isopropylaniline and 1,4-phenylene diamine(I). More Schiff-base ligands were prepared by condensation of 2,3-butandione with 2,6-diisopropylaniline; 2,4-6-trimethyl aniline and 4,4-diaminophenyl (benzidine)(II), and subsequent metathesis reaction with (DME)NiBr2. Bis(alpha diimine)nickel(II)dibromide complexes are suitable catalysts and are precursors for the polymerization of ethylene after activation with methylaluminoxane (MAO). In comparison with these complex analogs, mono-nickel-center catalysts, the new catalysts have much bigger molecules, illustrated by the distance between every two active centers (II and III). For bi-nickel-center catalysts, the catalyst's structural credibility had profound influence on the catalytic activity. When the substituent was diisopropyl; t-butyl or methyl, the catalysts demonstrated much higher catalytic activity than the corresponding mononickel-center catalysts. Catalyst (II) with phenyl bridge showed high activity compared with catalyst (III) with diphenyl bridge. The catalytic properties of these complexes and the character of the obtained polymers depend on the ligand structure of the used catalysts. Substituents on the arene moiety and/or the backbone of the ligand influence the polymerization reaction. Small aryl substituents result in the formation of low molecular weight oligomers, whereas bulky aryl substituents gave high molecular weight polyethylene. Catalysts are cheap and can be prepared easily with available starting material and stable in air. The effect of Al/ Ni ratio, of reaction time, variation of ethylene pressure, and the effect of temperature on catalyst performance will be discussed.
Ethylene polymerization was carried out by immobilization of rac-ethylenebis(1-indenyl)zirconium dichloride (Et(Ind) 2 ZrCl 2 ) and rac-dimethylsilylbis(1-indenyl)zirconium dichloride (Me 2 Si(Ind) 2 ZrCl 2 ) preactivated with methylaluminoxane (MAO) on calcinated silica at different temperatures. Polymerizations of ethylene were conducted at different temperatures to find the optimized polymerization temperature for maximum activity of the catalyst. The Me 2 Si bridge catalyst showed higher activity at the lower polymerization temperature compared to the Et bridge catalyst. The highest catalytic activities were obtained at temperatures about 50 °C and 70 °C for Me 2 Si(Ind) 2 ZrCl 2 /MAO and Et(Ind) 2 ZrCl 2 /MAO catalysts systems, respectively. Inductively coupled plasma-atomic emission spectroscopy results and polymerization activity results confirmed that the best temperature for calcinating silica was about 450 °C for both catalysts systems. The melting points of the produced polyethylene were about 130 °C, which could be attributed to the linear structure of HDPE.
Ethylene polymerization using catalysts based on binuclear phenoxyimine titanium halide complexes
European Polymer Journal, 2012
Nine new binuclear titanium halide complexes were obtained on the basis of first synthesized tetradentate bis-phenoxyimine ligand precursors with different bridge linkages, including sterically hindered ones, between imine groups. Their binuclear character is confirmed by molecular weights, measured using vapor phase osmometry, MALDI-ToF and diffusion coefficients as determined by NMR-DOSY method. Catalytic activities of catalytic systems on the basis of the binuclear bis-salicylaldimine titanium complexes in ethylene polymerization were investigated. The studied catalytic systems appeared to be rather highly active, (10-70 kg(PE)/[mmol(Ti)ÁMPaÁh]) and considerably more thermostable as compared to mononuclear analogs and made it possible to obtain polyethylenes of high and superhigh molecular weights. The effects of the bridge linkage between imine nitrogens and o-, p-substituents in the phenoxy-group were established.
Journal of Polymer Science Part A-polymer Chemistry, 2005
An iron oligomerization catalyst, [(2-ArNC(Me))2C5H3N]FeCl2 [Ar = 2,6-C6H3(F)2], was combined with rac-ethylene bis(indenyl)zirconium (IV) dichloride [rac-Et(Ind)2ZrCl2] to prepare linear low-density polyethylene (LLDPE) by the in situ copolymerization of ethylene. A series of LLDPEs with different properties were prepared by the alteration of the reaction temperature, Fe/Zr molar ratio, Al/(Fe + Zr) molar ratio, and reaction time. The structures of the polymers were characterized with differential scanning calorimetry, 13C NMR, gel permeation chromatography (GPC), and so forth. The melting points, crystallizations, and densities of the resulting products increased, and the average branching degree decreased, as the reaction temperature, Al/(Fe + Zr) ratio, and reaction time increased. The melting points, crystallizations, and densities of the polymers decreased, and the average branching degree increased, when the Fe/Zr ratio increased. The 13C NMR and GPC results showed that there were no unreacted α-olefins remaining in the resulting polymers because the percentage of low-molar-mass sections (C4–C10) of the oligomers obtained with this catalyst was very high (>70%). In addition, the formation of polymers with two melting points under different reaction conditions was examined in detail, and the results indicated that the two melting points of the polymers could be attributed to polyethylene with different branches. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 984–993, 2005
Ethylene polymerization catalyzed by diamide complexes of Ti(IV) and Zr(IV
Journal of Applied Polymer Science, 2008
In this research, we describe the application of the complexes o-C6H4(NSiMe3)2ZrCl2 (1), o-C6H4(NSiMe3)2TiBr2 (2), o-C6H4(NSiMe3)2TiCl2 (3), C2H4(NSiMe3)2ZrCl2 (4), in the ethylene polymerization with different Al/M ratios and temperatures. These complexes presented significant catalytic activities in the presence of methyaluminoxane (MAO) as cocatalyst and toluene as solvent, producing high molecular weight linear polyethylenes. Zirconium complexes were more active at 60°C and titanium complexes at 40°C. Zirconium complex (1) showed the best values of activity (347 kg PE/mol Zr h atm) for Al/Zr ratio of 340 and 60°C of temperature. In ethylene-1-hexene copolymerization, the best result was also reached with catalyst 1, at the same conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Polymerization of Ethylene with Catalyst Mixture in the Presence of Chain Shuttling Agent
Chemistry & Chemical Technology, 2012
Mixture of two catalysts in one reactor for ethylene/α-olefin copolymerization in the solution process can result in the combination of microstructures related to both catalysts in the polymer framework. Thus, novel polymer configuration is synthesized, which is characterized by containing sequences of monomers produced with each catalyst in the same polymer chain. Adding a reversible transfer agent (CSA) to the binary system enables the production of new block copolymers with enhanced properties. Late transition metal catalysts, such as α-diimine nickel catalyst when activated with methylaluminoxane (MAO) show high activity towards olefin polymerization and produces highly branched homopolymers. On the other hand, C 2 symmetry metallocene catalysts produce linear polyethylenes. This paper describes the synthesis of ethylene homopolymer with amorphous and crystalline blocks using a binary mixture containing a nickel catalyst with α-diimine ligand, which produces ф highly branched polyethylene (soft PE) and a metallocene (rac-ethylene bis(H 4-indenyl)ZrCl 2) that converts ethylene into polyethylene with high activities and melting temperatures (hard PE). The influence of polymerization temperature and CSA concentration were investigated. The polymeric materials were characterized by density, thermal properties, X-ray diffractometry and dynamic-mechanical properties.
Polymer Bulletin, 1989
Ethylene-propylene copolymerizations were carried out using conventional and high activity supported Ziegler-Natta catalysts to examine the reduction of Ti(III) to Ti(II) by aluminum alkyls, which has been considered as a main reason for the catalytic activity decay in propylene polymerization. For the catalyst system cocatalyzed with DEAC, the reduction was negligible regardless of the catalyst types, while an irreversible catalyst modification such as the reduction reaction occurred significantly for the catalyst with TEA.
European Polymer Journal, 2019
Catalysts play a pivotal role in the olefin polymerization process. After decades of development, a growing number of transition metal catalysts have been widely used in the field of olefin polymerization. Among them, the performance of catalysts such as nickel, titanium, vanadium and chromium are the most attractive. During catalysis process, the chemical valence of the metal in the catalysts usually changed and formed active center with unpaired electron at their outmost electron orbital. Electron Paramagnetic Resonance (EPR) is a good means to detect unpaired electron and free radicals and avoid distraction of other species such as co-catalyst, solvent, monomer etc. This paper reviews the recent progress in the preparation of branched polyethylene with nickel, titanium, vanadium and chromium catalytic systems and EPR analysis of related catalytic systems. Low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) are main branched polyolefin products which are currently being adopted for the usage at industrial scale [14-16]. At present, the preparation of polyolefin products is mainly obtained by radical polymerization [17] as well as ethylene homo-polymerization
Low density polyethylene by tandem catalysis with single site Ti(IV)/Co(II) catalysts
1 Over the past two decades, research has increasingly been directed towards the development of single-site catalytic systems, as they can produce polyethylenes (PE) with a tailored microstructure 2], especially in terms of branching control. Branching affects many properties of PE, such as density, rigidity, permeability, and environmental stress-crack resistance .
Single and binary catalyst systems based on nickel and palladium in polymerization of ethylene
Applied Organometallic Chemistry, 2017
The catalyst (N,N‐bis(2,6‐dibenzhydryl‐4‐ethoxyphenyl)butane‐2,3‐diimine)nickel dibromide, a late transition metal catalyst, was prepared and used in ethylene polymerization. The effects of reaction parameters such as polymerization temperature, co‐catalyst to catalyst molar ratio and monomer pressure on the polymerization were investigated. The α‐diimine nickel‐based catalyst was demonstrated to be thermally robust at a temperature as high as 90 °C. The highest activity of the catalyst (494 kg polyethylene (mol cat)−1 h−1) was obtained at [Al]/[Ni] = 600:1, temperature of 90 °C and pressure of 5 bar. In addition, the performance of a binary catalyst using nickel‐ and palladium‐based complexes was compared with that of the corresponding individual catalytic systems in ethylene polymerization. In a study of the catalyst systems, the average molecular weight and molecular weight distribution for the binary polymerization were between those for the individual catalytic polymerizations;...