Catalytic Systems For Ethylene Polymerization Research Articles

Novel titanium (IV) diolate complexes with thiophene-containing OSO-type ligand as pre-catalyst for ethylene polymerization and ethylene - propylene copolymerization

New titanium (IV) complexes with diolate ligand containing additional donor sulfur atom have been synthesized and characterized. Structure of complex 2 was established by X-ray diffraction. Titanium atom adopts a distorted tetrahedral geometry formed by oxygen atoms of two ligands and isopropoxy-groups. Activation of these complexes with {EtnAlCl3-n + Bu2Mg} led to a highly active catalytic system for ethylene polymerization with an activity up to 2 tons PE·molTi-1·atm-1·h-1. Linear ultrahigh molecular weight polyethylenes (1.9-5.7 106 Da) were obtained under these conditions. The obtained polyethylenes are suitable for the modern methods of polymer processing - the solventless solid state formation of super high-strength (breaking strength up to 2.6 GPa) and high-modulus (elastic modulus up to 164 GPa) oriented films and film tapes. The precatalysts 1-3 were also active in ethylene-propylene copolymerization producing copolymers with a content of propylene units in the range 28-33%. The influence of the nature of the «leaving» monodentate σ-ligands (Cl, OiPr and N(CH3)2) and the organoaluminum co-catalyst (Et2AlCl and Et3Al2Cl3) on the activity of catalytic systems and the properties of the resulting polymers were studied.

Pd-Iminocarboxylate Complexes and Their Behavior in Ethylene Polymerization.

Designing co-catalyst-free late transition metal complexes for ethylene polymerization is a challenging task at the interface of organometallic and polymer chemistry. Herein, a set of new, co-catalyst-free, single-component catalytic systems for ethylene polymerization have been unraveled. Treatment of anthranilic acid with various aldehydes produced four iminocarboxylate ligands (L1-L4) in very good to excellent yield (75-92 %). The existence of 2-((2-methoxybenzylidene)amino) benzoic acid (L1) has been unambiguously demonstrated using NMR spectroscopy, MS and single-crystal X-ray diffraction. A neutral Pd-iminocarboxylate complex [{N O}PdMe(L1)] (N O=κ2 -N,O-ArCHNC6 H4 CO2 with Ar=2-MeOC6 H4 ) C1 was prepared by treating stoichiometric amount of L1.Na with palladium precursor. The identity of C1 was confirmed by 1-2D NMR spectroscopy and single-crystal X-ray diffraction studies. Along the same lines, palladium complexes C2-C4 were prepared from ligands L2-L4 respectively. In-situ high-pressure NMR investigations revealed that these Pd complexes are amenable to ethylene insertion and undergo facile β-H elimination to produce propylene. These palladium complexes were then evaluated in ethylene polymerization reaction and various reaction parameters were screened. When C1-C4 were exposed to ethylene pressures of 10-50 bar, formation of low-molecular-weight polyethylene was observed.

DFT modeling of active particles with one and two Mg atoms in post-titanocene catalytic systems for ethylene polymerization

The DFT modeling of active particles in post-titanocene catalytic systems for ethylene polymerization suggests that catalytic centers with two magnesium atoms are more stable and more reactive with respect to ethylene as compared to the centers with one magnesium atom; this is in agreement with experimental data.

Synthesis of PE Wax by Chromium Complexes Bearing NP Ligands

AbstractThree binuclear chromium complexes stabilized by 1,5,9,13‐tetra(phosphinoamine)cyclohexadecane ligand were synthesized and characterized. In combination with TMA‐depleted methylalumoxane/triethylaluminium (DMAO/TEA) as cocatalyst, they generate active catalytic systems for ethylene polymerization to form ultra low molecular weight polyethylene (PE) wax with moderate catalytic activity in methylcyclohexane (MeCy). The molecular weight of PE wax is ranging from 612 to 841 g/mol with a narrow polydispersity (PD=1.37‐1.80). The effects of polymerization parameters, such as solvent, temperature, catalyst concentration, the ratio of cocatalyst on the catalytic activity and properties of the PE wax were also investigated.

Chain transfer reaction to diethylzinc in ethylene polymerization by metallocene catalysts

The addition of diethyl zinc into the metallocene catalytic system for ethylene polymerization efficiently reduces the molecular weight of the resulted polyethylene due to the transfer reaction of the propagation chain to the dialkyl zinc. The alkyl exchanging reaction between diethyl zinc and the methylaluminoxane or trimethyl aluminum may result in the new zinc compounds. Therefore, the result of regression analysis shows that the chain transfer is not an ideal first order reaction. The regression result also shows that the transfer reaction to zinc is much stronger than other transfer reaction. The reaction results in the long alkyl zinc, and the latter is easily be oxidized, and then forms the polyethylene contains an abundance of hydroxyl capped chain end, which has been identified by means of 13C-NMR.

Activation effect of metal chlorides in post-metallocene catalytic systems for ethylene polymerization: A DFT study

This work is devoted to the DFT study of the activation effect of metal chlorides (MgCl2, LiCl, ZnCl2, CaCl2) in ethylene polymerization reactions on post-titanocene complexes LTi(Y)Cl (1), where L is the bidentate saligenin type ligand, Y is alkyl group or Cl. The activation effect of metal chlorides is caused by secondary complexation reactions between 1 and metal chlorides. In accordance with previously reported experimental data, our DFT calculations predict that the most probable catalytic particles in the systems based on MgCl2 possess higher reactivity with respect to ethylene molecule than in the systems based on LiCl. One could expect a higher catalytic activity for CaCl2 than for MgCl2, but for ZnCl2 the catalytic activity should be the lowest. Results of our calculations show that at least three different hetero-trinuclear compounds of Ti, Mg and Al have similar reactivity towards ethylene molecule. This result explains Mw/Mn indexes >2 measured earlier for one of the systems under the study with R3Al (R = Me, t-Bu) as activators.

Synthesis, characterization, and ethylene polymerizations of various N–O chelated mono Cp ∗ titanium complexes

Various mono Cp ∗ type titanium mononuclear complexes ( 1– 5) and dinuclear complexes ( 6 and 7) containing non-Cp type chelate ligand, picolinate group, which has multi-binding sites of N and O atoms were synthesized and fully characterized by 1H and 13C NMR spectroscopy, mass spectroscopy, elemental analysis, and X-ray diffraction study. The 1 and 2/MMAO catalytic systems for ethylene polymerization exhibited a moderate activity and gave the polyethylenes with broad molecular weight distributions.

Benzophenone-functionalized, starlike polystyrenes as organic supports for a tridentate bis(imino)pyridinyliron/trimethylaluminum catalytic system for ethylene polymerization

Starlike polystyrenes composed of a microgel core and arms terminated with benzophenone groups were used as organic supports for a tridentate bis(imino)pyridinyliron catalyst for ethylene polymerization in the presence of trimethylaluminum as a cocatalyst. The microgels were synthesized by the atom transfer radical polymerization of styrene initiated by 4-(1-bromoethyl)-benzophenone, with divinylbenzene as the crosslinker. The bromine polystyrene chain ends prevented the ethylene polymerization reaction and had to be removed. This was readily achieved with Cu0 together with dodecanethiol as a transfer agent. When used as supports in the presence of trimethylaluminum and 2,6-bis[1-2,6(diisopropylphenyl)imino]ethylpyridynyl iron, these bromine-free, functionalized polystyrene stars enabled the production of polyethylene beads of a spherical morphology and high bulk density with a catalytic activity similar to that under homogeneous reaction conditions. Moreover, the molar mass distribution of the polyethylene was narrow, suggesting limited transfer to trimethylaluminum. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6997–7007, 2006

Functionalized Star‐Like Polystyrenes as Organic Supports of a Tridentate Bis(imino)pyridinyliron/Aluminic Derivative Catalytic System for Ethylene Polymerization

AbstractSummary: Star‐like polystyrenes composed of a microgel core with arms functionalized with a few hydroxy‐ or methoxy‐ended ethylene oxide units were used as organic supports for a tridentate bis(imino)pyridinyliron catalyst towards ethylene polymerization. When used as supports of 2,6‐bis[1‐2,6(diisopropylphenyl)imino]ethylpyridynyl iron dichloride in the presence of various alkylaluminium compounds, the supported catalysts enabled the production, with a high catalytic activity, of polyethylene beads of a spherical morphology and high bulk density. A good control of the polyethylene molar mass distribution could also be achieved, which was explained by a lowering of the transfer reaction to the aluminium derivative, as compared to homogeneous conditions.SEM image of PE particles prepared in the presence of trimethylaluminium supported on a PS microgel with an iron catalyst (TMA/Fe = 800).imageSEM image of PE particles prepared in the presence of trimethylaluminium supported on a PS microgel with an iron catalyst (TMA/Fe = 800).

Silica powder obtained by sol-gel method as a support of organometallic vanadium catalyst for ethylene polymerization

Sol-gel technique was employed to obtain the silica-type powder, which after modification procedure was applied as a support of organometallic catalytic system for ethylene polymerization. The powder product was synthesized using hydrolysis and condensation of TEOS, catalyzed by ammonia. Obtained material and a reference support (commercial silica Davisil) were characterized to determine their particle size distributions, BET surface area, pore volume and diameter. Gas-phase adsorption of vanadium catalyst on analyzed support materials as well as adsorption from the solution in hexane were carried out. Both carrier materials were thermally pretreated prior catalytic systems syntheses and the influence of modification method applied on resulting organometallic catalyst character was estimated in low-pressure slurry polymerization of ethylene. Obtained results prove that sol-gel material, due to its advantageous morphology with wide and shallow pores, allows to obtain catalytic systems of higher activity in low-pressure ethylene polymerization, in comparison with commercial silica Davisil.

A novel zirconocene/ultradispersed diamond black powder supported catalytic system for ethylene polymerization

A novel carrier of ultradispersed diamond black powder (UDDBP) was used to support metallocene catalyst. Al 2O 3 was also used as carrier in order to compare with UDDBP. Supported catalysts for ethylene polymerization were synthesized by two different reaction methods. One way was direct immobilization of the metallocene on the support, the other was adsorption of MAO onto the support followed by addition of the metallocene. Four supported catalysts Cp 2ZrCl 2/UDDBP, Cp 2ZrCl 2/Al 2O 3, Cp 2ZrCl 2/MAO/UDDBP and Cp 2ZrCl 2/Al 2O 3/MAO were obtained. The content of the zirconium in the supported catalyst was determined by UV spectroscopy. The activity of the ethylene polymerization catalyzed by supported catalyst was investigated. The influence of Al/Zr molar ratio and polymerization temperature on the activity was discussed. The polymerization rate was also observed.

Ni(acac)2-DAD/MAO: A new catalytic system for ethylene polymerization

Ni(acac)2-DAD/MAO: A new catalytic system for ethylene polymerization

Ni(acac)2-DAD/MAO: A new catalytic system for ethylene polymerization

The halide-free combination of Ni(acac) 2 and DAD(diazadiene, ArN=CH-CH=NAr, where Ar = 2,6-C 6 H 3 (i-Pr) 2 ) is active for ethylene polymerization in the presence of methylaluminoxane (MAO). The performance of this new catalytic system was evaluated with respect to activity and polymer structure. The degree of branching of the obtained polyethylenes is substantially influenced by the polymerization conditions. The activation mechanism was investigated by 'H NMR. MAO is proposed to participate in the ligand exchange process.

A Catalytic System for Ethylene Polymerization Based on Group III and Lanthanide Complexes of Tris(pyrazolyl)borate Ligands

We report here the synthesis and characterization of tris(3, 5-dimethyl-1-pyrazolyl)borohydride Tp{sup Me} complexes of yttrium of the general formula [Tp{sup Me}YR{sub 2}(THF){sub x}] [R = C{sub 6}F{sub 5}, CH{sub 2}SiMe{sub 3}]. We have found these complexes and similar ones of variously substituted Tp ligands, as well as analogous lanthanide complexes, to be active in the catalytic polymerization of ethylene to linear, extremely high molecular weight polymers. The variations in polymerization activity of polyethylene (PE) that are obtained from different members of this class of complexes show that synthetic tailoring allows control over the rate of polymerization reaction and the yield of the PE product. 10 refs., 1 fig., 1 tab.

Catalytic systems for ethylene polymerization

1. 1. Ethylene polymerization on catalytic systems obtained by the reaction of titanium trichloride with chlorinated aluminium or by joint chlorination of titanium and aluminium in benzene, has been studied. 2. 2. The direction of the process towards polymerization or alkylation depends on the molar ratio of Cl/Al in the heterogeneous phase of the catalyst. 3. 3. The properties of the polymer are similar to the properties of polyethylene obtained in the presence of a Ziegler catalyst.