The influence of cocatalysts on 1-hexene polymerization with various supported magnesium – titanium catalysts

Summary The influence of various cocatalysts on the activity and stereospecificity of a supported magnesium–titanium catalyst, generated by in situ reduction of titanium (IV) chloride using a Grignard reagent (MgCl₂/TiCl₃) or prepared by the recrystallization method (MgCl₂/2M2P/ED/TiCl₄, 2M2P= 2-methyl-2-pentanol, ED= dibutyl phthalate or ethyl benzoate), in the 1-hexene polymerization was investigated. The MgCl₂/TiCl₃ catalyst showed the highest activity but the lowest stereospecificity in the 1-hexene polymerization with all investigated cocatalysts. The MgCl₂/2M2P/ED/TiCl₄ catalyst with dibutyl phthalate as an internal electron donor was characterized by the highest stereospecificity and led to the polymers with high molecular weight. All catalysts showed the highest activity and stereospecificity when triisobutylaluminium was used as a cocatalyst. The addition of a small amount of ethyl benzoate as an external electron donor ([Al]/[ED] 10:1) led to considerable improvement of the stereospecificity of the MgCl₂/TiCl₃ catalyst in comparison with the catalysts prepared by the recrystallization method.     

Effects of Ti oxidation state on ethylene, 1-hexene comonomer polymerization by MgCl<Subscript>2</Subscript>-supported Ziegler–Natta catalysts

In this study, the influences of the Ti oxidation state on the catalytic properties of MgCl₂-supported Ziegler–Natta catalysts in ethylene homo- and co-polymerization with 1-hexene were investigated. Three catalysts having different Ti oxidation states were synthesized by milling TiCl₄, TiCl₃, or TiCl₂ together with MgCl₂. With these catalysts having different Ti oxidation states, the polymerization conditions such as the Al concentration, temperature, and 1-hexene concentration were varied to figure out their catalytic abilities in ethylene homo- and co-polymerization. The Ti oxidation state affected the catalyst activity largely, having unique dependences on the polymerization conditions. A higher oxidation state led to a higher activity, slightly larger comonomer incorporation, and lower molecular weight as well as its narrower distribution. However, rough characteristics of copolymers were similar among the different Ti oxidation states.     

Preparation of soluble TiCl3 catalysts by reduction of TiCl4 with Grignard reagents and their use for copolymerization of ethylene with propylene

Summary Preparations of soluble TiCl₃ catalysts by reduction of TiCl₄ with some types of Grignard reagents were carried out in halogenated hydrocarbon solvents by using appropriate ethers as donor. The soluble TiCl₃·MgX₂·ether complex catalysts and triisobutylaluminum as co-catalyst showed high activities for the copolymerization of ethylene with propylene. It was first found that the soluble TiCl₃·MgX₂·ether complex catalysts enhance the activities for the copolymerizations in the same manner as solid titanium catalysts supported on MgCl₂ which show high activities for homopolymerizations of olefin monomers. The copolymers obtained possessed low crystallinities. Also, the copolymers seem to contain microblock sequences and have outstandingly high tensile strength and elongation at break compared to copolymers by the conventional VOCl₃/Al(Et)_1.5Cl_1.5 catalyst system.     

New crystalline complex chlorides containing transition metal chlorides or oxychlorides as components of coordination catalysts

Novel complex chlorides have been obtained by reacting TiCl₄, VOCl₃, MoOCl₄, WOCl₄, or AlCl₃, with Be, Mg, Ca, or Sr chlorides in the presence of electron donors such as POCl₃ (L) or C₆H₅POCl₂, (L′). The resulting products, obtained with good yield, show defined stoichimetry, ionic character, and crystalline structure, and may be considered reference systems for high-yield catalysts in the low-pressure polymerization of ethylene (HDPE). Complexes (TiCl₆)MgL₆, (TiCl₅L′)₂ MgL′₆, and (Ti₂Cl₁₀)MgL₆ associated with (i-C₄H₉)₃Al were found very active in HDPE synthesis, but completely unable to polymerize propylene. This result and other evidence suggest that part of the catalytic activity of these systems is displayed by soluble species. The role played by the Mg ion in high-yield catalysts is displayed by soluble species. The role played by the Mg ion in high-yield catalysts is discussed in the light of the peculiar behavior shown by the complex chlorides containing this earth-alkali metal.     

Novel binary chlorides containing TiCl3 as components of coordination catalysts for ethylene polymerization. II. Behavior of the resulting catalyst systems

Binary chlorides described in part I yielded very active catalyst systems for HDPE synthesis when they were associated with (i-C₄H₉)₃Al. Very high initial polymerization rates were observed for systems bases on MnCl₂·TiCl₃, MnCl₂·2TiCl₃, or FeCl₂·2TiCl₃ (III), but high yields, i.e., above 30 kg polymer/g Ti, could be reached only using moderate pressure of ethylene. Hydrogen consumption during ethylene polymerization was observed in the case of catalysts based on AlCl₃·3TiCl₃, CrCl₃·3TiCl₃, and other binary chlorides containing elements of the VIII group. Relevant amounts of ethane were found in the case of systems III, V, and VIII. All the mixed chlorides studied were able to reduce cyclohexene in the presence of H₂ and (i-C₄H₉)₃Al, even though with different kinetic courses. Compounds II, III, V, and VIII and (MgCl₂)_1.5·TiCl₃ and AlCl₃·3TiCl₃ were very active. The results have been explained on the basis of solubilization processes involving the heterogeneous catalysts which actually were experimentally verified during cyclohexene reduction. Analogous processes may occur also during HDPE synthesis.     

Catalytic activity and control of the nascent morphology of polyethylenes obtained with first and second generation of Ziegler–Natta catalysts

The morphologies of the as-produced polyethylenes obtained by slurry polymerization process of ethylene in n-heptane, using heterogeneous conventional and supported Ziegler–Natta catalysts, were investigated. The ability of four different catalytic systems in controlling the size and shape of the nascent polymer particles were tested. The catalytic systems employed were: the original Ziegler type catalyst produced by reduction of TiCl₄ with Et₂AlCl, the Natta type catalyst TiCl₃–AA, the reduced TiCl₄ with the metal carbonyls [Mo(CO)₆ and Mn₂(CO)₁₀], and the supported TiCl₄ on three commercial silicas having different surface areas: Davison 951, 952, and also the Dart 1000. It was found that the carriers affect the catalytic activity of the final catalyst and also its kinetic behavior. The supported Ziegler–Natta catalysts control more easily the nascent polymer particles (size, shape, and porosity) than the conventional ones. In addition the morphology of the catalysts and the subsequent polymer particles are closely related to the parent morphology of the silicas used as carriers. Furthermore, the nascent morphology of the polyethylenes obtained with the conventional TiCl₄–Et₂AlCl catalytic system can be modified by using different |Al|/|Ti| ratios, resulting in more dense, spherical, and bigger polymer particles by increasing this ratio. On the other hand, detailed studies on the texture or arrangement of the polymer particles reveal the existence of mainly two fine morphologies (globular and wormlike), which are the result of the order of the primary or elementary catalyst particles (microspheres and platelets), the force linking them together, and the activity of the polymerization centers placed on their surface.     

Theoretical study of Ziegler-Natta olefin polymerization mechanisms on heterogeneous catalysts and on homogeneous catalysts by using ``PIO' analysis and ``LFO' calculation

Polymerization mechanisms on O_h- propyltitaniumchlorides and T_d- propyltitaniumchlorides, active site models of TiCl₃ catalysts and metallocene catalysts, respectively, are studied by using ``paired interacting orbitals' (PIO) analysis and ``localized frontier orbitals' (LFO) calculation. In the case of TiCl₃ catalysts the possible route of an incoming ethylene is constrained by Cl anions located in the ethylene insertion plane. In the case of metallocene catalysts, such a constraint does not appear, and therefore, they should be superior to TiCl₃ catalysts in catalytic activity. The low reactivities of TiCl₃ catalysts are removed considerably by making Ti_2n clusters on the crystalline surface. This revised version was published online in July 2006 with corrections to the Cover Date.     

Highly active catalysts for ethylene polymerization by the reduction of TiCl4 with organomagnesium compounds

The effect of introducing metal halides other than AlCl₃ into a TiCl₃ catalyst, by the reduction of TiCl₄ with various metal alkyls is examined. Magnesium halides are shown to be most effective in increasing catalyst activity for the polymerization of ethylene. The influence of the type of organomagnesium compound on catalyst activity is studied, together with the effect of reaction conditions in the reduction step. The composition and structure of the catalysts is discussed. The results show conclusively that the activity of a TiCl₃ catalyst in the Ziegler polymerization of ethylene is strongly affected by the presence of other metal compounds.     

With different structure ligands heterogeneous Ziegler-Natta catalysts for the preparation of copolymer of ethylene and 1-octene with high comonomer incorporation

Comparison with the conventional Ziegler-Natta catalyst TiCl₄/MgCl₂ (I), the modified supported Ziegler-Natta catalysts (iso-PentylO)TiCl₃/MgCl₂ (II) and (BzO)TiCl₃/MgCl₂ (III) were prepared as efficient catalysts for copolymerization of ethylene with 1-octene. The complexes (II) and (III) were desirable for the production of random ethylene/1-octene copolymers coupled with higher molecular weight, higher comonomer incorporation within copolymer chain and good yield even at high temperature 80 ^°C and fairly low Al/Ti molar ratio of 100. The effects of catalysts ligands, Al/Ti molar ratio, polymerization temperature, as well as concentration of 1-octene on the catalytic activity, molecular weight and microstructure of the copolymer were investigated in detail. The structure and properties of the copolymers were characterized with ¹³C NMR, GPC, DSC and WAXD. The kinetic results also indicate that these catalysts (II) and (III) show higher catalytic activity and the produced polymers feature higher molecular weight, because of lower ratio of K_trm/K_p and K_tra/K_p, and higher ratio of K_tra/K_trm which indicates that chain transfer to cocatalyst is predominant.     

Synthesis of cis‐1,4‐polyisoprene with Al‐Ti catalysts modified by different electron donor reagent

The preparation of the high cis ?1,4‐polyisoprene by Ziegler‐Natta catalysis system was studied. The effect of Al‐Ti catalysts modified by ethers with different structures which are different electron donor reagent on polymerization of isoprene has been mainly investigated. By the measurement method of the monomer conversion, FTIR, and ¹H NMR spectroscopy, the influence of, respectively, added diphenyl ether, anisole, dibutyl ether, or methyl tert ‐butyl methyl ether as a third active component on the heterogeneous TiCl₄‐Al(i ‐Bu)₃‐ether catalyst activity and microstructure of synthetic polyisoprene was analyzed. By the adding of diphenyl ether or dibutyl ether, the process of prefabricated heterogeneous catalyst is quickly and catalyst particle quantity is large. The polymerization conversion is high and the microstructure cis ?1,4 content of the resulting polymer can reach 92%. But Al(i ‐Bu)₃ added anisole or methyl tert ‐butyl methyl ether hard to cooperate with TiCl₄. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 44357.     

Surface science studies of Ziegler-Natta olefin polymerization system: Correlations between polymerization kinetics, polymer structures, and active site structures on model catalysts

The surface composition and structure of model Ziegler-Natta catalysts, polymerizing α-olefins to produce polyolefins, have been studied using modern surface science techniques and compared with their polymerization behaviors. Two types of thin films — TiCl_x/MgCl₂ and TiCl_y/Au — were fabricated on an inert gold substrate, using chemical vapor deposition methods, to model the high-yield catalysts of MgCl₂-supported TiCl₄ and TiCl₃-based catalysts, respectively. The model catalysts could be activated by exposure to triethylaluminum (AlFt₃) vapor. Once activated, both catalysts were active for polymerization of ethylene and propylene in the absence of excess AlEt₃ during polymerization. The model catalysts had polymerization activities comparable to the high-surface-area industrial catalysts. Though both catalysts were terminated with chlorine at the surface, each catalyst assumed different surface structures. The TiCl_x/MgCl₂ film surface was composed of two structures: the (001) basal plane of these halide crystallites and a non-basal plane structure. The TiCl_y/Au film surface assumed only the non-basal plane structure. These structural differences resulted in different tacticity of the polypropylene produced with these catalysts. The TiCl_x/MgCl₂ catalyst produced both atactic and isotactic polypropylene, while the TiCl_y/Au catalyst without the MgCl₂ support produced exclusively isotactic polypropylene. The titanium oxidation state distribution did not have a critical role in determining the tacticity of the polypropylene.     

Polymerization of propylene by highly active catalysts synthesized with Mg(OEt)2/benzoyl chloride/TiCl4

Summary Active centers have been studied in the polymerization of propylene using highly active Mg(OEt)₂/Benzoyl chloride/TiCl₄ catalysts activated with AlEt₃. The method for the measurement of active centers is based on the inhibiting effect of CO on polymerization. The activity of the present catalysts, which is higher than that of TiCl₃ or MgCl₂-supported catalyst, is mainly due to the higher concentration of active centers by one order of magnitude. In order to investigate the stability of active centers during polymerization the number of active centers are compared at various polymerization times.     

Synthesis mechanisms of poly[styrene‐co‐(acrylic acid)]‐supported TiCl4 catalysts modified by magnesium compounds

Soluble poly[styrene‐co‐(acrylic acid)] (PSA) modified by magnesium compounds was used to support TiCl₄. For ethylene polymerization, four catalysts were synthesized, namely PSA/TiCl₄, PSA/MgCl₂/TiCl₄, PSA/(n‐Bu)MgCl/TiCl₄, and PSA/(n‐Bu)₂Mg/TiCl₄. The catalysts were characterized by a set of complementary techniques including X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and element analysis. Synthesis mechanisms of polymer‐supported TiCl₄ catalysts were proposed according to their chemical environments and physical structures. The binding energy of Ti 2p in PSA/TiCl₄ was extremely low as TiCl₄ attracted excessive electrons from ? COOH groups. Furthermore, the chain structure of PSA was destroyed because of intensive reactions taking place in PSA/TiCl₄. With addition of (n‐Bu)MgCl or (n‐Bu)₂Mg, ? COOH became ? COOMg‐ which then reacted with TiCl₄ in synthesis of PSA/(n‐Bu)MgCl/TiCl₄ and PSA/(n‐Bu)₂Mg/TiCl₄. Although MgCl₂ coordinated with ? COOH first, TiCl₄ would substitute MgCl₂ to coordinate with ? COOH in PSA/MgCl₂/TiCl₄. Due to the different synthesis mechanisms, the four polymer‐supported catalysts correspondingly showed various particle morphologies. Furthermore, the polymer‐supported catalyst activity was enhanced by magnesium compounds in the following order: MgCl₂ > (n‐Bu)MgCl > (n‐Bu)₂Mg > no modifier. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

High activity mixed metal alkyl cocatalysts for α-olefin polymerization

High activity α-olefin polymerization catalysts are generally obtained by mixing MgCl₂-supported TiCl₄ (MgCl₂/TiCl₄) with an aluminum trialkyl cocatalyst. Surprisingly, AlEt₂Cl, which is the preferred cocatalyst in polymerizations employing nonsupported Ti compounds, is a poor cocatalyst when used with MgCl₂/TiCl₄. It was found that in propylene and 1-butene polymerizations, using different MgCl₂/TiCl₄ catalysts, the cocatalyst activity of AlEt₂Cl can be greatly improved by the addition of a magnesium or lithium alkyl. The mixed metal alkyl obtained from AlEt₂Cl and MgBu₂ is a particularly effective cocatalyst always yielding more polymer, of about the same stereospecificity, than the conventional aluminum trialkyls. The exact nature of the mixed metal alkyl cocatalysts is not known, but the available evidence argues against in situ aluminum trialkyl formation resulting from the alkylation of AlEt₂Cl by the second metal alkyl.     

Kinetics of ethylene polymerization at high temperature with Ziegler–Natta catalysts

A kinetic technique is developed for the study of ethylene polymerization reaction at high temperature with Ziegler–Natta catalysts. The technique is based on the calculation of polymerization rate parameters from the data on ethylene consumption vs. time. It takes into account increase of reaction temperature at the beginning of the reaction. Kinetic data in coordinates “polymerization rate–time” are presented for several pseudohomogeneous catalysts (TiCl₄? AlEt₂Cl, Ti(OiC₃H₇)₄? AlEt₂Cl), heterogeneous catalysts (δ-TiCl₃? AlEt₃, δ-TiCl₃? AlEt₂Cl, TiCl₄/MgCl₂? AlEt₃, TiCl₄/MgCl₂? AlEt₂Cl) and solubilized catalysts (δ-TiCl₃? poly-1-hexene? AlEt₂Cl) at 180°C and reaction pressure 14.6 atm for first 10 min of the reaction. These data are useful for the selection of Ziegler–Natta catalysts for testing in ethylene polymerization reaction in continuous high pressure reactors at short residence times.     

Butadiene polymerization with vanadium–titanium–aluminum catalytic systems

Butadiene polymerization in the presence of mixed vanadium–titanium–aluminum catalytic systems containing various organoaluminum compounds (OACs) was investigated. The main factors influencing the activity and stereospecificity of the [VOCl₃–TiCl₄–OAC₁]–(heating)–OAC₂ catalysts [where OAC₁ and OAC₂ were Al(i‐Bu)₃, Al(i‐Bu)₂H, or Al(i‐Bu)₂Cl] were considered. The kinetic parameters of the process were determined. The high activity and stereospecificity of the multicomponent systems probably accounted for the formation of polymerization active sites with both transition‐metal derivatives in their structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 211–217, 2004     

Novel binary chlorides containing TiCl3 as components of coordination catalysts for ethylene polymerization. I. Synthesis and characterization of the solid solutions obtained

New binary chlorides have been obtained by reacting TiCl₄ with V(CO)₆, Cr(CO)₆, Mn₂(CO)₁₀, Mn(CO)₅Cl, Ni(CO)₄, Co₂(CO)₈, Fe(CO)₅, or Mo(CO)₆. The reactions yield quantitatively mixed chlorides having the general formula MCl_n·n TiCl₃, where n = 2 or 3 and M is a divalent or trivalent transition metal cation. MCl_n is generally isomorphous with the α- or γ-modification of TiCl₃. X-Ray and spectroscopic investigations indicate that the mixed chlorides obtained are solid solutions. High surface area values are associated with the adducts displaying lower crystallinity. Catalyst efficiencies two or three times higher than that of AlCl₃·3TiCl₃ were observed in the low-pressure polymerization of ethylene (HDPE) when some binary chloride was associated with Al(i-C₄H₉)₃. These results allow treating the obtained solid solutions as reference systems of high-yield catalysts for HDPE synthesis.     

The influence of some synthesis parameters on Ziegler-Natta catalyst performance

Catalysts based on TiCl₃ modified by di-n-butyl ether (DBE) as internal base were synthesized with the aim to obtain polypropylene particles of controlled morphology. Two routes were used to synthesize the catalysts (System A and System B). In System A, DBE employed as internal base was complexed with TiCl₄ and diethylaluminum chloride (DEAC) in iso-octane solution and in System B, DBE was complexed with triethylaluminum (TEA) and TiCl₄ in toluene solution. The catalysts were evaluated in propylene polymerization and the polymer morphology was characterized by optical and scanning electron microscopies, bulk density and particle size distribution.     

Melamine-Formaldehyde-Supported Titanium-Based Heterogeneous Ziegler-Natta Catalyst for Ethylene Polymerization in Slurry Process

Ethylene was polymerized at 40°C temperature and 1 atm. pressure using melamine-formaldehyde (M-F) supported titanium tetrachloride (TiCl₄) catalyst. Polymer-supported catalysts were prepared with a different weight ratio of TiCl₄/ M-F in hexane. The wt% titanium incorporated in the polymer matrix was determined by UV-visible spectroscopy. In addition, the resulting catalysts were characterized by SEM-EDX, XRD, and TGA. The catalytic productivity is found to be 4721.09 g PE/g Ti/h. The productivity of the catalysts also depends on the titanium content in the polymer matrix. The catalyst with titanium content 3.5 wt% showed maximum activity. These catalysts also showed good storability.     

Macrokinetics of Polybutadiene Production on a Titanium Ziegler–Natta Catalyst System Prepared in Turbulent Flows

The research was directed at establishing the dependence of the disperse composition of particles of TiCl₄–Al(i-C₄H₉)₃ catalytically active precipitate, and their activity and molecular weight characteristics of polybutadiene formed in their presence on the length of sections and the confuser diameter of the tubular turbulent apparatus of diffuser–confuser design used to prepare a catalytic system in turbulent flows. An approach that combines methods of computational fluid dynamics (ANSYS Workbench 17.1 platform) and formal kinetics, and solves inverse problems of kinetics has been used to solve the stated problem. The following required dependences were established based on numerical experiments on the models developed using this approach: (1) the hydrodynamics of the process of dispersing particles of TiCl₄–Al(i-C₄H₉)₃ catalytically active precipitate in a tubular turbulent apparatus with diffuser–confuser design, and (2) macrokinetics of butadiene polymerization on the particles of TiCl₄–Al(i-C₄H₉)₃ catalytically active precipitate dispersed in turbulent flows (batch reactor, the solvent was toluene, and the temperature of the process was 25°С).