Polymerization of propylene with TiCl3–AlEt2Cl–trilauryltrithiophosphite catalyst

AlEt₃Cl was modified with TLTTP (trilauryltrithiophosphite) in the catalyst system consisting of TiCl₃ and AlEt₂Cl. The effects of TLTTP on the polymerization of propylene were studied in comparison with those of alkyl homologues of TLTTP. The catalytic behavior of the TiCl₃–AlEt₂Cl-TLTTP catalyst system in the polymerization of propylene was also studied in comparison with that of the TiCl₃–AlEt₂Cl catalyst system. In the study of the effect of various alkylthiophosphites added, it is found that the bulkiness of the alkyl group affects the rate of propylene polymerization and the stereoregularity of the resultant polymers. The TiCl₃–AlEt₂Cl–TLTTP catalyst system gave different catalytic behavior in the propylene polymerization from that of the unmodified conventional catalyst system (TiCl₃–AlEt₂Cl). These effects of TLTTP were considered to be due to the bulkiness of the alkyl groups attached to the phosphorous atom and the higher reactivity to TiCl₃ of the modified AlEt₂Cl than of the unmodified AlEt₂Cl.     

Preparation of bimodal polypropylene in two‐step polymerization

Polymerization of propylene was carried out by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system in n‐heptane, where MgCl₂, EtOH, TiCl₄, DIBP (diisobutyl phthalate), TEA (triethyl aluminum), and cHMDMS (cyclohexyl methyl dimethoxy silane) were support, ethanol for alcoholation, catalyst, external donor, cocatalyst (activator), and internal donor, respectively. The catalyst activity and polymer isotacticity were studied by measuring the produced polymer and its solubility in boiling n‐heptane, respectively. The molecular weight and molecular weight distribution of the polymers were evaluated by gel permeation chromatography. Hydrogen was used for controlling the molecular weight. For producing the bimodal polypropylene, the polymerization was carried out in two steps (i.e., in the presence and absence of hydrogen). It was found that the catalyst showed high activity and stereoselectivity, on the other hand, bimodal polymer could simply be produced in two‐step polymerization by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system. Meanwhile, the effect of the step of the hydrogen adding on propylene polymerization was investigated. It was shown that the addition of hydrogen in the second step was more suitable. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1456–1462, 2006     

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.     

Kinetics study of slurry-phase propylene polymerization with highly active Mg(OEt)2/benzoyl chloride/TiCl4 catalyst

Propylene was polymerized in a slurry phase over superactive and stereospecific catalyst prepared by the reaction of Mg(OEt)₂ with benzoyl chloride and TiCl₄ in the presence of AlEt₃ with or without an external donor. A kinetic analysis of propylene polymerization was carried out. The polymerization rate was first order with respect to monomer concentration and the dependence of overall polymerization rate on the concentration of AlEt₃ can be explained by the Langmuir adsorption mechanism. Maximum activity was observed around an Al/Ti mole ratio of 20. The average rate over 90 min of polymerization as a function of temperature showed a maximum around 42°C and the overall activation energy was 8.5 kcal/mol at T < 42°C and ?4.0 kcal/mol at T > 42°C. The analysis of the phenomenon of an optimum temperature gave 2.2 kcal/mol for the activation energy of the rate-determining step, and 6.3 kcal/mol, for the adsorption energy of AlEt₃. The addition of small amount of p-ethoxyethyl benzoate (PEEB) as an external donor increased the percentage of isotactic polymer to 98% and slightly increased activity in spite of the decrease in the concentration of active centers due to the stabilizing effect of the active centers by the external donor. The temperature showing maximum yield was shifted to the higher temperature when AlEt₃ and PEEB ([AlEt₃]/[PEEB] = 5) was used as a cocatalyst. © 1994 John Wiley & Sons, Inc.     

Butyl chloride as promoter in ethylene polymerization by magnesium ethoxide‐supported catalyst

The effects of butyl chloride as a promoter in the ethylene polymerization were studied using a Mg(OEt)₂/TiCl₄/triethyl aluminum (TEA) Ziegler–Natta catalyst system, where Mg(OEt)₂, TiCl₄, TEA were used as support, catalyst, and activator, respectively. The influence of BC on the catalyst performance, polymerization rate, and polymer properties were investigated. This study strongly indicates that BC could act as a promoter with high performance in the ethylene polymerization. There was a remarkable increase in the catalyst yield and polymerization rate, in particularly, in the presence of hydrogen which was used for controlling the molecular weight. A reduction in the polymer molecular weight was observed in the presence of BC and hydrogen. The morphology of the polymers was evaluated through scanning electron microscopy and particle size distribution. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40189.     

Kinetic and morphological study of a magnesium ethoxide‐based Ziegler–Natta catalyst for propylene polymerization

BACKGROUND: Kinetic and morphological aspects of slurry propylene polymerization using a MgCl₂‐supported Ziegler–Natta catalyst synthesized from a Mg(OEt)₂ precursor are investigated in comparison with a ball‐milled Ziegler–Natta catalyst. RESULTS: The two types of catalyst show completely different polymerization profiles: mild activation and long‐standing activity with good replication of the catalyst particles for the Mg(OEt)₂‐based catalyst, and rapid activation and deactivation with severe fragmentation of the catalyst particles for the ball‐milled catalyst. The observed differences are discussed in relation to spatial distribution of TiCl₄ on the outermost part and inside of the catalyst particles. CONCLUSION: The Mg(OEt)₂‐based Ziegler–Natta catalyst is believed to show highly stable polymerization activity and good replication because of the uniform titanium distribution all over the catalyst particles. Copyright © 2008 Society of Chemical Industry     

Ethylene and propylene polymerization catalyzed by a model Ziegler-Natta catalyst prepared by gas phase deposition of magnesium chloride and titanium chloride thin films

Model Ziegler-Natta catalysts are prepared by gas phase deposition of ultra-thin TiCl₄/ MgCl₂ films in UHV conditions. A monolayer of TiCl₄ chemisorbed on a solid solution of titanium and magnesium chloride is formed in this way. The reduction and alkylation of TiCl₄ by its reaction with a liquid layer of AlEt₃ condensed on the halide film is monitored by XPS. Most of the TiCl₄ is reduced by AlEt₃ and is incorporated in the mixed titanium /magnesium chloride. The model catalyst is active in the polymerization of ethylene and propylene at 300 K, both in the absence and in the presence of AlEt₃ in the reaction cell. The polymers that form over the catalyst film have been characterized by Raman spectroscopy. The weak signals from methyl end groups and unsaturations suggest high molecular weight for both polymers. The polypropylene film has a high degree of isotacticity even without the use of any electron donor. For the propylene polymerization reaction the overall turnover frequency is in the range between 0.1 and 1 molecule/(site s).     

Copolymerization of propylene with 1‐octene catalyzed by MgCl2/TiCl4/diether catalyst

MgCl₂/TiCl₄/diether is a fifth‐generation Ziegler–Natta catalyst for the commercial polymerization of propylene. The outstanding features of this catalyst are the high activity and high isotacticity for propylene polymerization without using an external electron donor. In this study, we explored the copolymerization of propylene and 1‐octene with MgCl₂/TiCl₄/diether catalyst. It was found that MgCl₂/TiCl₄/diether catalyst showed higher polymerization activity and led to greater 1‐octene content incorporation, compared with a fourth‐generation Ziegler–Natta catalyst (MgCl₂/TiCl₄/diester). With an increase in 1‐octene incorporation in polypropylene chains, the melting temperature, glass transition temperature and crystallinity of the copolymers decreased distinctly. The microstructures of the copolymers were characterized using ¹³C NMR spectroscopy, and the copolymer compositions and number‐average sequence lengths were calculated from the dyad concentration and distribution. This result is very important for the in‐reactor polyolefin alloying process, especially for the case of a single catalyst and two‐step (or two‐reactor) process. Copyright © 2011 Society of Chemical Industry     

Interaction of α-TiCl3 with organoaluminium compounds and its correlation with propylene polymerization

Summary The kinetics of the interaction between the catalyst components of a Ziegler-Natta sterospecific system formed by TiCl₃ and AlEt₃ in heptane was studied. The experimental results show that the rate of propylene polymerization is influenced by the rate of the interaction, activation energy, and the efficiency of interaction.     

Microstructure of isotactic polypropylene obtained using Ziegler–Natta catalyst at high polymerization temperature

The microstructure of the isotactic polypropylene obtained with various MgCl₂‐supported catalyst systems at high polymerization temperature of 70–100°C is investigated by discussing the intrinsic relation between the different types of active centers and the polymerization temperatures via gel permeation chromatography, temperature rising elution fractionation, and ¹³C NMR. For the MgCl₂/TiCl₄/di‐n‐butyl phathalate‐AlEt₃/external donor and MgCl₂/TiCl₄/2,2‐diisobutyl‐1,3‐dimethoxypropane‐AlEt₃ catalyst systems, the differences in the isotactic productivity of polymers obtained at different polymerization temperatures mainly result from the variation of both the activity of the different isospecific active centers and the stability constants of the complex of catalyst/donor. The reaction rate of high isotactic active centers reaches maximum at 85–90°C, and this effect contributes to both the highest isotacticity and the narrowest molecular weight distribution. For the MgCl₂/TiCl₄/phthalate ester‐AlEt₃ catalyst system, the isotacticity of polypropylene remains approximately constant in the temperature range of experiments, which could be ascribed to elution of phthalate ester after the activation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42487.     

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.     

Synthesis of highly isotactic poly 1-hexene using Fe-doped Mg(OEt)2/TiCl4/ED Ziegler–Natta catalytic system

In this article, polymerization of 1-hexene with FeCl_3-doped Mg(OET)₂/TiCl₄/electron donor (ED) catalytic system is presented. For this purpose, first a number of TiCl₄ catalysts supported on Mg(OEt)₂ and Fe-doped Mg(OEt)₂ supports were prepared with ethylbenzoate or dibutylphthalate as the internal EDs. After successive catalysts synthesis, they were employed in 1-hexene polymerization using cyclohexyl methyl dimethoxysilane as external ED as well as without it. The catalysts activity and molecular weight distribution (MWD) of poly 1-hexenes (PHs) were influenced strongly by both FeCl₃ doping and donor presence so that a remarkable increase in the catalyst activity was seen in doped catalysts. Deconvolution of MWD curves revealed that increase in the type of active centers by introducing FeCl₃ into the support should be responsible for the broadening of MWD of PHs. ¹³CNMR analysis indicated that while isotacticity does not change considerably by Fe doping, EDs increase its amount as high as 8–21%. Second, the stereoselective behavior of active Ti species in doped and undoped catalysts was fully explored by molecular modeling using density functional theory (DFT) method. Finally, with the aid of rheological measurements, the processability of polymers were evaluated and then the gel permeation chromatography (GPC) results were approved through the values obtained from model fitting as well as changes in moduli crossover modulus.     

Solubility of 1‐hexene in LLDPE synthesized by (2‐MeInd)2ZrCl2/MAO and by Mg(OEt)2/DIBP/TiCl4–TEA

The solubility of 1‐hexene was measured for linear low‐density polyethylenes (LLDPEs) produced over a heterogeneous Ziegler–Natta catalyst, Mg(OEt)₂/DIBP/TiCl₄–TEA (ZN), and over a homogeneous metallocene catalyst, (2‐MeInd)_zZrCl₂–MAO (MT). The 1‐hexene solubility in LLDPEs was well represented by the Flory–Huggins equation with a constant value of χ. ZN–LLDPEs dissolved a larger amount of 1‐hexene and thus showed a lower value of χ compared to MT–LLDPEs. The Flory–Huggins interaction parameter χ, or the solubility of 1‐hexene at a given temperature and pressure, was suggested as a sensitive measure for the composition distribution of LLDPEs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1566–1571, 2002; DOI 10.1002/app.10418     

Kinetic study on propylene polymerization by a high activity catalyst system: MgCl2/TiCl4/PhCO2Et-AlEt3/PhCO2Et

Summary Kinetic study was performed in short time propylene polymerization with a high activity-high stereospecificity catalyst system composed of MgCl₂/TiCl₄/PhCO₂Et with AlEt₃/PhCO₂Et. The concentration of the active centers, [C ^*], the propagation rate constant, k _p, and the chain transfer rate, r _tr, were determined. The change of these values by the change of polymerization conditions, the concentration of monomer, AlEt₃, and the temperature, were studied.     

Nature of Phthalates as Internal Donors in High Performance MgCl2 Supported Titanium Catalysts

High performance MgCl₂ supported titanium catalyst having diisobutyl phthalate (DIBP) as internal donor has been synthesized. The organic components present in the catalyst have been studied through FTIR, 1D and 2D NMR spectroscopy. The results indicate presence of diethyl phthalate also in addition to DIBP. WAXD analysis has been done to study the features of MgCl₂ crystallites. Impact of donor components on the catalyst preparation leading to reaction pathways and performance for propylene polymerization has been evaluated.     

Comonomer enhancement effect of 1-hexene in ethylene copolymerization catalyzed over MgCl2/THF/TiCl4 catalysts

Homo- and copolymerization of ethylene were performed by using a catalyst system composed of TiCl₄/THF/MgCl₂ complex activated with AlEt₃ at 70°C and 3 atm. To investigate the effect of the compositional difference of the catalyst on the rates of homo- and copolymerization and on the reactivity in ethylene–hexene copolymerization, a series of six catalysts with different compositions (Mg/Ti = 0.4–16.5) were prepared by coprecipitation. The catalytic activity in ethylene polymerization increased sharply with the Mg/Ti ratio from 21 (Mg/Ti = 0.4) to 1477 kg PE/g-Ti h (Mg/Ti = 16.5). The activity in copolymerization with 1-hexene also increased with Mg/Ti ratio. The values of r₁ were 120, regardless of Mg/Ti ratios within the experimental error range. Enhancement of the polymerization rate by the addition of 1-hexene in the reaction medium was observed only for the catalysts of low Mg/Ti ratio. This unusual effect of 1-hexene on the polymerization rate was explained by chemical and physical processes that occurred during polymerization. © 1993 John Wiley & Sons, Inc.     

The effect of different process parameters on the TiCl4/internal donor/MgCl2/AlEt3 catalytic system using external donor and cyclohexylchloride

In this work, the effects of different process parameters were investigated on the performance of TiCl₄/internal donor/MgCl₂/AlEt₃ catalytic system and produced polyethylene in a semi-batch stirred reactor. Various methods such as Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscope (SEM), sieve shaker and melt flow index (MFI) measurement were used to investigate the catalyst activity and final polyethylene product. The results showed that cyclohexylchloride as promotor, in the presence of external donor, increased the catalyst activity up to 110% at optimum ratio to titanium. On the other hand, the polymer particle size and fine particles, which were directly related to the catalyst activity in the most cases, increased up to 15% in the presence of optimal halocarbon/Ti ratio and decreased up to 45% using hydrogen in the studied range. Also, in the optimal ratio, cyclohexylchloride increased the active site concentration and as a result, the MFI increased significantly. Also at low agitator speeds, due to low heat and mass transfer, the catalyst particles were severely fragmented and the particle size was decreased clearly. The results also showed that due to the special catalyst structure, pre-polymerization with propylene increased the catalyst activity by approximately two times compared to ethylene pre-polymerization.

     

Propylene polymerization with δ-TiCl3/AlClEt2 and δ-TiCl3/AlEt3 catalyst systems

Summary Some parameters of propylene polymerization using -TiCl₃/AlClEt₂ and -TiCl₃/AlEt₃ catalyst systems were evaluated. The catalyst was prepared through the reduction of TiCl₄ complexed with di-n-butyl ether (DBE) (mole ratio DBE/TiCl₄=0.67) by AlClEt₂. Propylene polymerizations were carried out at different Al/Ti ratios, using AlEt₃ or AlClEt₂ as cocatalysts and different polymerization temperatures. The effects of these parameters on catalyst activity, stereo-specificity and polymer molecular weight were investigated. The results indicate that these parameters strongly affect catalyst performance.     

Preparation of highly active supported catalysts for producing polypropylene with less content of chloride

Summary Highly active supported catalysts for propylene polymerization have been prepared by treating the complexes of TiCl₃· 3C₅H₅N and MgCl₂·(THF) with AlEt₂Cl in the presence of MgO, Mg(OH) ₂ ^x or SiO₂. Polypropylene with less content or chloride was produced over these catalysts combined with AlEt₃.     

Propylene polymerization by using TiCl4 catalyst supported on solvent‐activated Mg(OEt)2

Solvent activation of Mg(OEt)₂ in ethanol with carbon dioxide was carried out in a 1‐L three‐neck flask under nitrogen atmosphere, to investigate structural changes of Mg(OEt)₂ support. During activation of Mg(OEt)₂ by ethanol and CO₂, a suspension mixture was converted to a clear solution and CO₂ was inserted into the Mg? O bond of Mg(OEt)₂, to form magnesium ethyl carbonate. The solid supports were obtained from the removal of solvents by heating, during which CO₂ split off from the magnesium ethyl carbonate between 100 and 150°C. The structural changes of the obtained supports and the corresponding catalysts were checked by IR and TGA. The polymerization behavior of propylene with the catalyst and morphology of the obtained polymer were also examined. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 460–467, 2001