Polymerization of propylene using a prepolymerized high-active Ziegler–Natta catalyst. I. Kinetic studies

The kinetics of propylene polymerization using a prepolymerized high-active TiCl₃ catalyst with an Et₂AICI cocatalyst are investigated. The effect of various parameters such as AI/Ti ratio, pressure, temperature, hydrogen, and polymerization time on the rate of polymerization and yield are examined. The dependency of these parameters on the polymerization rate are studied. It is found that the variation at the rate of polymerization with the Et₂AICI cocatalyst concentration complies with a Langmuir–Hinshelwood type of relationship. The overall activation energy of polymerization calculated from the Arrhenius plot was found to be 11.6 kcal/mol. © 1996 John Wiley & Sons, Inc.     

Effect of high polymerization temperature on the microstructure of isotactic polypropylene prepared using heterogeneous ticl4/mgcl2 catalysts

The effects of alkylaluminum and polymerization temperature on propylene polymerization without an external donor in the use of a TiCl₄–MgCl₂–diether(BMMF) catalyst were investigated. The results indicated that with increasing polymerization temperature the concentrations of [mmmm] of heptane‐insoluble poly(propylene) (PP) fraction increased. Crystallization analysis fractionation (CRYSTAF) results showed the fractions of different crystallization temperatures were changed according to various polymerization temperatures. The activity with Et₃Al as cocatalyst at 100°C was much lower than that at 70°C. However, the activity with i‐Bu₃Al at 100°C was as high as that at 70°C. The fraction of high‐crystallization temperature of PPs obtained with i‐Bu₃Al increased with increasing polymerization temperature, which was opposite to that with Et₃Al, thus implying that the copolymerization of propylene with the monomer arising from Et₃Al led to the lower crystallization ability of PPs obtained with Et₃Al. The terminal groups of PP suggested that the chain‐transfer reaction by β‐H abstraction was the main chain‐transfer reaction at 120°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3980–3986, 2003     

Investigation of kinetics of 4‐methylpentene‐1 polymerization using Ziegler–Natta‐type catalysts

The kinetics of 4‐methylpentene‐1 (4MP1) polymerization by use of Ziegler–Natta‐type catalyst systems, M(acac)₃‐AlEt₃ (M = Cr, Mn, Fe, and Co), are investigated in benzene medium at 40°C. The effect of various parameters such as Al/M ratio, reaction time, aging time, temperature, catalyst, and monomer concentrations on the rate of polymerization and yield are examined. The rate of polymerization increased linearly with increasing monomer concentration with first‐order dependence, whereas the rate of polymerization with respect to catalyst concentration is found to be 0.5. For all cases, the polymer yield is maximum at an Al/M ratio of 2. The activation energies obtained from linear Arrhenius plots are in the range of 25.27–33.51 kJ mol^?1. It is found that the aging time to give maximum percentage yield of the polymer varies with the catalyst systems. Based on the experimental results, a plausible mechanism is proposed that envisages a free‐radical mechanism. Characterization of the resulting polymer product, for all the cases, through FTIR, ¹H‐NMR, and ¹³C‐NMR studies, showed isomerized polymeric structures with 1,4‐structure as dominant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2468–2477, 2003     

<Emphasis Type="Italic">m</Emphasis>-Cresol-substituted triethyl aluminum/MoCl<Subscript>5</Subscript>/TBP catalytic system for coordination polymerization of butadiene

Coordination polymerization of butadiene was initiated by a catalyst system consisting of tributyl phosphate (TBP) as ligand, molybdenum pentachloride as primary catalyst and triethyl aluminum substituted by m-cresol as co-catalyst. The effects of the substitution of m-cresol on the activity of the catalyst system, molecular weight and molecular weight distribution, intrinsic viscosity and microstructures of the resulting polymers were investigated in details. The molecular weight and molecular weight distribution of the polymerization products were determined by GPC. The microstructure of the polymerization products was characterized by FTIR, ¹³C NMR and DSC techniques. The experimental results indicated that the polymerization activity of the reaction system and the molecular weight of the polymerization products gradually increased with the increase of the substitution content of m-cresol, namely, Al(OPhCH₃)₂Et?>?Al(OPhCH₃)Et₂?>?Al(OPhCH₃)_0.5Et_2.5>AlEt₃. The 1,2-structure contents of the polymerization products could be adjusted between 89 and 91% through the control of the substitution of m-cresol, and there was minute quantities of crystalline structures in the resulting polymers due to the increasing content of the syndiotactic 1,2-polybutadiene. In a word, the existence and increase of steric hindrance of m-cresol made it easier for polymerization products to form interdisciplinary 1,2-structure.     

Polymerization of olefins through heterogeneous catalysis,I. Low pressure propylene polymerization in slurry with Ziegler–Natta catalyst

Propylene was polymerized in slurry over a TiCl₃·? AICI₃ (Stauffer Type AA) catalyst with Al—Et₂Cl cocatalyst at 60 psig pressure both with and without H₂ present. The effects of polymerization temperature, catalyst poisons, and type of slurry liquid were investigated, with particular emphasis on the yield, tacticity, and MWD of the resulting polymer. The highest yields and isotactic content were obtained with decane–heptane mixtures as a slurry liquid, while slurry liquids in which polypropylene was most soluble gave the narrowest MWD.     

Gas phase polymerization of 1,3‐butadiene with supported neodymium‐based catalyst: Investigation of molecular weight

The gas phase polymerization of 1,3‐butadiene (Bd), with supported catalyst Nd(naph)₃/Al₂Et₃Cl₃/Al(i‐Bu)₃ or/and Al(i‐Bu)₂H, was investigated. The polymerization of Bd with neodymium‐based catalysts yielded cis‐1,4 (97.2–98.9%) polybutadiene with controllable molecular weight (MW varying from 40 to 80 × 10⁴ g mol^?1). The effects of reaction temperature, reaction time, Nd(naph)₃/Al(i‐Bu)₃ molar ratio, and cocatalyst component on the catalytic activity and molecular weight of polymers were examined. It was found that there are two kinds of active sites in the catalyst system, which mainly influenced the MW and molecular weight distribution of polybutadiene. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1945–1949, 2004     

A supported titanium postmetallocene catalyst: Effect of selected conditions on ethylene polymerization

Ethylene polymerization with a titanium complex [N,N‐ethylenebis(3‐methoxysalicylideneiminato)titanium dichloride] immobilized on the magnesium support with the formula MgCl₂(THF)_0.32(Et₂AlCl)_0.36 was studied. In particular, the effects of polymerization temperature, monomer pressure, and polymerization time on the activity of the catalyst and on the polyethylene properties (molecular weight and its distribution, melting point, crystallinity, and bulk density) were evaluated. The findings of investigations prove that the studied supported titanium catalyst is highly active in ethylene polymerization, and its activity increases with increasing temperature and monomer pressure. Moreover, stability of the catalytic systems is dependent on the activator type used. Me₃Al, when employed as an activator, makes the catalytic system undergo no deactivation in practice. The catalyst coupled with MAO turned out less stable. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Cationic polymerization of 2,4,4-trimethyl-2-oxazoline

Summary The cationic homopolymerization of 2,4,4-trimethyl-2-oxazoline using BF₃Et₂O as initiator at different initiator concentrations, temperatures, times and solvents of polymerization were carried out. The effect of these variables on the polymerization yield and viscosity of the polymers were studied. Polymers were characterized by IR.¹H NMR and¹³C NMR which support that the polymerization reaction occurs by ring opening of oxazoline through oxazolinium intermediates.     

Synthesis and characterization of EPDM films

A series of ethylene–propylene-2-ethylidenebicyclo[2.2.1]hept-5-ene terpolymers have been prepared using the VOCl₃/Al₂Et₃Cl₃ catalyst under various initial Al/V ratios and diene concentrations. The V/C and Al/V ratios in EPDM films were determined by Rutherford backscattering spectrometry. The concentration of incorporated vanadium increases with the increase of the iodine number, i.e., with the number of double bonds in the polymer. However, the concentration of incorporated V in the terpolymers remains relatively low, which is attributed to the small percentage of V(III) active species due to the presence of the diene. On the other hand, the Al/V molar ratio in the terpolymers was seen to be roughly constant (between 6 and 8), independent of the iodine number and of the initial Al/V molar ratio in the reaction mixture. The polymerization yield was seen to increase with the augmentation of the initial Al/V ratio and of the diene concentration, until reaching a maximum of about 500 g polymer/g V. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 535–541, 1998     

Comparative study of homogeneous and heterogeneous styrene polymerizations with Ni(acac)2/MAO catalytic system

Styrene polymerization was carried out with Ni(acac)₂/MAO and Ni(acac)₂/SiO₂/MAO. The influence of reaction parameters (Al/Ni mole ratio, catalyst concentration, temperature and time polymerization) on styrene polymerization was evaluated. It was observed that both catalytic systems were affected by reaction parameters and that the heterogeneous catalyst presented higher activity than the homogeneous one. Polystyrenes with different molecular weight, stereoregularity and polydispersity were obtained. These results suggest that different active catalyst species could have been present. In addition, two types of methylaluminoxane (MAO) with different molecular weights were also evaluated as cocatalyst. As a result, the catalyst activity and stereospecificity were strongly affected by the MAO type.     

Supported titanium catalysts based on magnesium dichloride—silicon tetraethoxide adduct for propylene polymerization

Anhydrous magnesium dichloride was reacted with silicon tetraethoxide to form a solid adduct. The adduct was treated with titanium tetrachloride and an internal Lewis base to prepare supported titanium catalysts. Alkyl benzoate (PhCOOR, R = Me, Et, n - Bu) or dialkyl phthalate [Ph(COOR)₂, R = Me, Et, n - Bu] was used as an internal Lewis base. The prepared catalysts (MT) in combination with triethylaluminum as a cocatalyst polymerize propylene to yield polypropylene. The nature and concentration of internal Lewis base influence the composition, specific surface area, and performance of the catalysts. The addition of diphenyl dimethoxysilane into the MT/Et₃Al catalyst system increases the isotactic index of polypropylene from 75 to 97 at a Si/Al mol ratio of 0.05. The overall results indicate that a dialkyl phthalate-incorporated catalyst shows better physical, chemical, and polymerization characteristics compared to a corresponding alkyl benzoate catalyst. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1445–1450, 1997     

Influence of diphenyl ether and water on the polymerization of isoprene with triisobutylaluminium and titanium tetrachloride

In the polymerization of isoprene with the i-Bu₃Al/TiCl₄ catalyst at the mole ratio of 1.0 the diphenyl ether adduct of the i-Bu₃Al showed no effect on the catalyst efficiency. The ether did not improve the low efficiency of the catalyst at ratios slightly above 1.0, but below 1.0 it brought the catalyst activity up to optimum. The ether compensated for the deleterious effects upon the catalyst of low amounts of water present in the isoprene solution in hexane. At the Al/Ti mole ratio slightly above 1.0, water and diphenyl ether were found to act synergistically in raising catalyst efficiency. In addition, at or close to optimal operating Al/Ti mole ratios the diphenyl ether had a very marked effect in improving the polymerization rate. Polymer properties were generally unaffected by use of the ether-coordinated catalyst.     

Highly active MgO-supported TiCl4 catalyst for the ethylene polymerization

Summary The MgO-supported TiCl₄ catalysts prepared by heating MgO with TiCl₄ showed a high activity for the ethylene polymerization in combination with Et₃Al or i-Bu₃Al. In these highly active catalysts, it has been shown that MgCl₂ is formed in the MgO-TiCl₄ reaction and is considered to contribute to the enhancement of the activity of the catalysts.     

A stacked neural network approach for yield prediction of propylene polymerization

Prediction of reaction yield as the most important characteristic process of a slurry polymerization industrial process of propylene has been carried out. Stacked neural network as an effective method for modeling of inherently complex and nonlinear systems–especially a system with a limited number of experimental data points–was chosen for yield prediction. Also, effect of operational parameters on propylene polymerization yield was modeled by the use of this method. The catalyst system was Mg(OEt)₂/DIBP/TiCl₄/PTES/AlEt₃, where Mg(OEt)₂, DIBP (diisobutyl phthalate), TiCl₄, PTES (phenyl triethoxy silane), and triethyl aluminum (AlEt₃) (TEAl) were employed as support, internal electron donor (ID), catalyst precursor, external electron donor (ED), and co‐catalyst, respectively. The experimental results confirmed the validity of the proposed model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Propylene polymerization in slurry catalyzed by titanium trichloride–diethyl aluminum chloride

Propylene is polymerized in a slurry over a TiCl₃ · ?AlCl₃ catalyst with a DEAC cocatalyst, approaching conditions of industrial relevance. The effects of various parameters such as temperature, pressure, cocatalyst-to-catalyst ratio, hydrogen concentration, and polymerization time are investigated with particular emphasis on the yield, tacticity, molecular weight, bulk density, and particle size of the resulting polymer. The highest yield and isotactic content are obtained at an Al/Ti ratio of 6, temperature of 70°C, and pressure of 9 kg/cm²g. The polymerization rate is found to be first order up to a monomer concentration of 2.5 mol/L. The overall activation energy of polymerization calculated from an Arrhenius plot is found to be 11.6 kcal/mol. A correlation between MFI and molecular weight is also presented. © 1994 John Wiley & Sons, Inc.     

The determination of active centres in olefin polymerisation

The kinetics of Ziegler-Natta polymerisations can be described in terms of a spectrum of active sites, each with differing propagation rates and stereospecificity. It is therefore necessary to use complementary methods of measuring active centres to get the whole picture. Higher activity in polymerisation of propylene using TiCl₃ - Et₂AlCl systems can be achieved by varying the catalyst preparation so that the effective surface area is increased or by removing inhibitors. When Et₃Al is used as activatior in place of Et₂ AlCl higher activity is due to a combination of increase in number of centres per mole TiCl₃ and of increase in their propagation rate.     

Butadiene polymerization with nickel compounds: Effect of cocatalysts

The preparation of a high cis-1,4-polybutadiene, using a novel ternary catalyst system composed of triethylaluminum, a soluble nickel compound, and boron trifluoride diethyl etherate has been reported in the literature. The present paper reports the polymerization results obtained when the triethylaluminum was replaced with other alkylaluminums and the BF₃ · Et₂O was replaced with other BF₃ complexes or HF · Et₂O. When utilizing BF₃ · Et₂O, both the polymerization rate and the polymer DSV decreased significantly as the length of the alkyl group in the alkylaluminum increased from C₁ to C₆. However, the length and nature of the alkyl group had virtually no effect when utilizing BF₃ · phenolate (BF₃ · 2C₆H₅OH) and only a small effect with HF · Et₂O; although the length of the alkyl group had no significant effect when using BF₃ complexes of aromatic aldehydes, the branched alkyl groups gave greater polymerization rates than did the corresponding n-alkyls. In summary, the strongly acidic complexes, BF₃ · phenolate and HF · etherate, promoted rapid polymerization when employed with any of the alkylaluminums. However, with other BF₃ complexes, the alkylaluminum selected had an important influence upon either the conversion and/or the polymer DSV.     

Polymerization of butadiene with Co(acac)3–(i-Bu)3Al–H2O catalyst

The polymerization of butadiene in toluene using Co(acac)₃–(i-Bu)₃Al–H₂O catalyst system was studied. Presented are the effects of the addition order, aging time, and composition of catalysts on rates, polymer microstructure, and molecular weights. The polymerization was found to be initiated by the Co(acac)₃-hydrolized aluminum alkyl complex. The chain propagation proceeds according to a first-order reaction with respect to monomer and active species and is a strong function of Al/H₂O with an optimum ratio of 1.0, but independent of Al/Co. The nature of polymerization seems to change as Al/H₂O increases from less than 1 to greater than 1. Transfer reaction is significant. From the kinetic data it was found that the termination reaction is most likely to be by combination.     

Effect of an external donor upon chain-transfer reactions in propylene polymerization with a MgCl2-supported titanium catalyst system

The chain-end groups of the polypropylene (PP) polymerized without addition of molecular hydrogen over a MgCl₂·TiCl₄·dioctylphthalate/Et₃Al catalyst system consisted of n-butyl, n-propyl, vinylidene and vinyl groups in addition to ethyl and i-butyl groups which were detected in the PP prepared under the same polymerization conditions except for the addition of diphenyldimethoxysilane (DPDMS) as an external donor. The newly detected chain-end groups indicate that the additional chain-transfer reactions were brought about by Et₃Al at 2,1-inserted sites and by β-hydrogen elimination at both 1,2- and 2,1-inserted sites. These chain-transfer reactions could account for the observed drops of the activity and the molecular weight in the absence of DPDMS. In addition, the detected chain ends in the PP polymerized with addition of molecular hydrogen over this catalyst system having no DPDMS suggest that the molecular hydrogen addition leads not only to the conversion of the dormant 2,1-inserted sites into the active sites, but also to a decrease in the frequency of 2,1-insertion.     

Polymerization of olefins through heterogeneous catalysis. XVII. Experimental study and model interpretation of some aspects of olefin polymerization over a TiCl4/MgCl2 catalyst

Using a high-activity MgCl₂-supported TiCl₄ catalyst, kinetic studies of ethylene and propylene polymerization are conducted in a semi-batch gas phase stirred-bed reactor system. Based on the experimental observations obtained from this study and others in the literature, simple kinetic mechanisms are proposed to explain the data. This model considers both the site formation from the interaction of catalyst and cocatalyst as well as the participation of monomers during site activation. By using this model together with parameters estimated from various sources, some aspects of kinetic behavior have been successfully predicted. These include the rate enhancement introduced by α-olefins, the effect of the Al/Ti ratio on kinetic features such as catalyst activity and decay rate, as well as the different reaction orders observed for various monomers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1037–1052, 1997