Zirconium Dichloride Catalyst Research Articles

Propylene Polymerization using Dimethylsilanediylbis[2-methyl-4-(4-tert-butylphenyl)-1-indenyl] Zirconium Dichloride/Methylaluminoxane Catalyst System Immobilized on Sylopol 643 and Sylopol 633

Two different commercial silica materials including Sylopol 643 and Sylopol 633 were used as support materials for the preparation of heterogenous dimethylsilanediylbis[2-methyl-4-(4-tert-butylphenyl)-1-indenyl] zirconium dichloride catalyst. The support materials were calcinated at two different temperatures under heating rate of 2 °C/min before treatment with methylaluminoxane (MAO). The effects of molecular hydrogen and Al/Zr ratio on polymer properties were considered. The catalyst system derived from Sylopol 643 exhibits higher catalyst activity than that of Sylopol 633. Uniform immobilization of MAO is achieved using Sylopol 643. Polymer particle growth characteristics and particle distribution depends strongly on the silica support used. Sylopol 633 produced higher fine level than Sylopol 643.

Copolymerization of ethylene/5‐ethylidene‐2‐norbornene with bis (2‐phenylindenyl) zirconium dichloride catalyst: I. Optimization of the operating conditions by response surface methodology

AbstractIn this study, the copolymerization of ethylene with nonconjugated diene (5‐ethylidene‐2‐norbornene) was carried out with a bis(2‐PhInd) ZrCl2 metallocene catalyst. Some polymerization factors that were considered affective on the catalyst activity, including comonomer content in the feed, ethylene pressure, and polymerization temperature, were investigated via response surface methodology to determine the optimum polymerization conditions. We found that the comonomer content in the feedstock had no enormous effect on the catalyst activity depression. Also, the polymerization temperature increment through the scrutinized range decreased the copolymerization activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Control of morphology in olefin polymerization catalyzed by nickel diimine complexes encapsulated into polybutadiene based support

A commercially available hydroxyl terminated low molecular cis-1,4-polybutadiene was modified by carboxylic functions and used as an effective support in single-site α-olefin polymerization. Dynamic light scattering analysis of support solution in heptane confirmed increased ability to self-assembly of modified polybutadienes in the presence of methylaluminoxane cocatalyst (MAO). α-Diimine nickel and bis(indenyl)zirconium dichloride catalysts activated by trimethylaluminium or MAO cocatalysts were encapsulated into polymer micellar aggregates and used for ethylene and octadec-1-ene polymerization. Furthermore, the effects of cocatalyst type and concentration on the micelle-formation process, activity and morphology of polyethylene (polyoctadec-1-ene) particles were investigated. In the presence of polybutadiene supports, formation of spherical micrometric PE beads was observed during MAO cocatalyzed ethylene polymerization, whereas the activity of polymerization was not decreased.

Influence of cocatalyst on the stereoselectivity and productivity of styrene polymerization reactions

Influence of different cocatalysts on the polymerization reaction of styrene using heterogeneous nanoparticle NA-MgO and NA-TiO2 (anatase) supported bis (cyclopentadienyl) zirconium dichloride catalysts is studied. Methyaluminoxane, trityl tetrakis(pentafluorophenyl)borate(1), dimethylanilinium tetrakis (pentafluoro-phenyl)borate (2) and tris(pentafluorophenyl)borane (3) are used as cocatalysts for this study. The productivity and stereoselectivity of the catalysts systems are found to be highest with MAO and lowest with the borane 3 (MAO > 1> 2 > 3). Catalysts derived from the borane 3 yield amorphous atactic polystyrenes but those from cocatalysts MAO, 1, or 2 yield crystalline, syndiotactic polystyrenes under the same reaction conditions. Effects of addition of various scavengers and solvents with different polarities on styrene polymerizations are also reported here. Characterization of the obtained polymers is done by Gel Permeation Chromatography, 13C-NMR spectroscopy and Differential Scanning Calorimetry.

Investigation of styrene/1‐hexene copolymerization by homogeneous and heterogeneous bisindenyl ethane zirconium dichloride catalyst system

AbstractHomogeneous copolymerization of styrene and 1‐hexene was carried out in toluene at room temperature using bisindenyl ethane zirconium dichloride/methylaluminoxane (MAO). The supported catalyst was prepared with immobilization of Et(Ind)2ZrCl2/MAO on silica (calcinated at 500°C) with premixed method. Heterogeneous copolymerization of styrene/1‐hexene with different mole ratios was carried out in the presence of supported catalyst system. The copolymers obtained from homogeneous and heterogeneous catalyst system were characterized by 1H NMR and 13C NMR. Composition of the resulting copolymers was determined by 1H NMR data. Analysis of 13C NMR spectra of obtained copolymers by homogeneous and heterogeneous catalyst systems present isotactic olefin‐enriched copolymers. Molecular weight and thermal behavior of resulting copolymers was investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4008–4014, 2007

Ethylene/1‐octene copolymerization studies with in situ supported metallocene catalysts: Effect of polymerization parameters on the catalyst activity and polymer microstructure

AbstractEthylene and 1‐octene copolymerizations were carried out with an in situ supported rac‐[dimethylsilylbis(methylbenzoindenyl)] zirconium dichloride catalyst. In a previous study, it was found that some in situ supported metallocenes produced polyethylene/α‐olefin copolymers with broad and bimodal short chain branching distributions and narrow molecular weight distributions. The ability to produce polyolefins with multimodal microstructural distributions in a single metallocene and a single reactor is attractive for producing polymers with balanced properties with simpler reactor technology. In this study, a factorial experimental design was carried out to examine the effects of the polymerization temperature and ethylene pressure, the presence of hydrogen and an alkylaluminum activator, and the level of the comonomer in the feed on the catalyst activity, short chain branching distribution, and molecular weight distribution of the polymer. The temperature had the most remarkable effect on the polymer microstructure. At high 1‐octene levels, the short chain branching distribution of the copolymer broadened significantly with decreasing temperature. Several factor interactions, including the hydrogen and alkylaluminum concentrations, were also observed, demonstrating the sensitivity of the catalyst to the polymerization conditions. For this catalyst system, the responses to the polymerization conditions are not easily predicted from typical polymerization mechanisms, and several two‐factor interactions seem to play an important role. Given the multiple‐site nature of the catalyst, it has been shown that predicting the polymerization activity and the resulting microstructure of the polymer is a challenging task. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4426–4451, 2002

Polyethylene synthesis using zeolite as support for metallocene catalyst

Zeolite sodic mordenite was evaluated as support for bis(cyclopentadienyl) zirconium dichloride catalyst in the synthesis of polyethylene. The zeolite was calcinated at 300°C under heating rate of 2°C/min before treatment with methylaluminoxane (MAO) and Cp 2ZrCl 2 solutions. The supported catalysts were prepared under different conditions of Cp 2ZrCl 2 impregnation temperature and MAO and Cp 2ZrCl 2 concentrations. The performance of the heterogeneous catalyst systems was evaluated in terms of polymerization activities and the characteristics of the produced polyethylene. Although not expected, it was observed in this work that high amounts of zirconium incorporated on the support leaded to catalysts with lower catalyst activity. The obtained polyethylene with these supported catalysts presented very high molecular weights.

Synthesis and activity of zirconocene catalysts supported on silica-type sol-gel carrier for ethylene polymerization

Synthesis and activity of bis(cyclopentadienyl)zirconium dichloride catalyst supported on unconventional silica-type material obtained in sol-gel process and activated by organoaluminium co-catalyst were studied. The effect of support modification conditions (thermal dehydration and/or modification by organoaluminium compound) and a type of co-catalyst on an activity of the catalytic system in ethylene polymerization and properties of resulting polymers were investigated and compared with results obtained earlier for vanadium catalysts supported on mentioned sol-gel carrier. The most appropriate method of the sol-gel silica-type support preparation is thermal pre-treating (200°C) followed by modification with AlEt2Cl. Metallocene catalyst supported on such sol-gel product and activated by MAO appeared to be most active among studied systems. Studied Cp2ZrCl2/MAO supported on silica-type sol-gel carrier allow to obtain polyethylene (at 50°C polymerization temperature) with yield up to 30·106 g/(molZr·h), molecular weight below 300 000 and MWD=2−4.

Kinetics, polymer molecular weights, and microstructure in zirconocene-catalyzed 1-hexene polymerization

1-Hexene was polymerized by rac-(dimethylsilyl)bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride catalyst and methylaluminoxane cocatalyst over the temperature range 0-100 °C. The polymerization rate, polymer molecular weight, and polymer microstructure (stereospecificity and regiospecificity) were studied as a function of the temperature and the concentrations of monomer, catalyst, and cocatalyst.

Influence of activators on ethylene polymerization with diphenylmethylidene-(cyclopentadienyl)(fluorenyl)zirconium dichloride catalysts at high temperature

Ethylene polymerization was carried out with diphenylmethylidene-(cyclopentadienyl)(fluorenyl)zirconium dichloride (Ph2C(Cp)(Flu)ZrCl2) activated with various activators such as methylaluminoxane (MAO), tetrakis(pentafluorophenyl)borates (R·B(C6F5)4, R=Me2PhNH, Ph3C, C7H7, H(Et2O)n), dimethylanilinium tetrakis(pentafluorophenyl)aluminate (Me2PhNH·Al(C6F5)4) and tris(pentafluorophenyl)borane (B(C6F5)3) to study the correlation between catalyst performance for ethylene polymerization and cocatalysts at high temperature. R·B(C6F5)4-activated catalysts showed relatively high activity but Al(C6F5)4-activated catalyst showed very low activity, presumably due to the low thermal stability. B(C6F5)3-activated catalyst also indicated low activity. This activity difference reflected the relative coordinative abilities of the anions and tightness of the ion-pairing. MAO-activated catalyst was comparable in activity and copolymerization reactivity with Me2PhNH·B(C6F5)4-activated catalyst and these two catalyst produced high molecular weight ethylene/1-hexene copolymers in a high pressure process.

Regioirregular Propene Insertion in Polypropenes Synthesized with Unbridged Bis(2-aryl)indenyl Zirconium Dichloride Catalysts: Implications on Activity

Catalysts of the type bis(2-(3,5-R 2 C 6 H 3 )indenyl)zirconium dichloride/MAO (2, R = H; 3, R = CF 3 ) were investigated for regioregularity of monomer insertion in bulk propene polymerization and compared to the isospecific catalyst rac-(ethene)bis(indenyl)zirconium dichloride/MAO (1). The amount of regioirregular propene insertions were in the range of 0.1-0.5 mol % and followed the trend 2 < 3 < 1. Comparison of polymerizations in the presence and absence of hydrogen revealed a 4-10-fold increase in productivity for catalysts 2 and 3 in the presence of hydrogen but only a slight increase in productivity with 1. For catalysts 2 and 3, only 2,1-erythro internal regioerrors were observed, whereas 1 produced both 2,1-erythro and 2,1-threo misinsertions. Evidence for ethene insertion following a 2,1-regioerror was obtained by copolymerization of 13 C 2 H 4 with propene using catalyst 3. The correlation between number of 2,1-misinsertions and catalyst activity is discussed.

Synthesis and polymerization behavior of tetrahydro-2-methylbenzindenyltitanium and zirconium compounds

In order to further our study of the bis(2-methylbenz[ e]indenyl)zirconium dichloride catalyst system, we have synthesized the analogous tetrahydro-2-methylbenz[ e]indene ligand ( 4). In the process of synthesizing 4, we have found that the structural isomer tetrahydro-2-methylbenz[ f]indene ( 5) is also formed. This has been confirmed by the synthesis of a series of dimethyl ( 6 and 7), methyl-phenyl ( 8), and titanium trichloride derivatives ( 11 and 12) of the parent indenes 4 and 5. The new ligand systems 4, 6, 7, and 8 were converted to the analogous unbridged zirconocene dichloride complexes 13, 14, 15, and 16. The precursors were then activated with either methylaluminoxane (MAO) or triphenylcarbenium tetrakis(pentafluorophenyl)borate (trityl) and used as catalysts for the polymerization of ethylene and propylene. All zirconocene complexes were highly active for the polymerization of ethylene, and in some cases produced crystalline polypropylene at lower polymerization temperatures.

Steric and electronic effects of R in (2-(4-R-C 6H 4)indenyl) 2ZrCl 2 catalysts on the synthesis of elastomeric polypropylene

Metallocene catalysts derived from bis(2-arylindenyl)zirconium dichloride catalysts yield elastomeric stereoblock polypropylene. A study of the steric and electronic effects of varying the 4-substituent of bis(2-(4-R-C 6H 4)indenyl)zirconium dichloride [( 1 RH, 2 RMe, 3 REt, 4 R nBu, 5 R tBu, 6 RSiMe 3, 7 RCF 3, 8 RCl)] on propylene polymerization at 25, 50, 75 psig and bulk propylene revealed that the polymerization behavior of these catalysts is not strongly influenced by the nature of the substituent in the 4-position of the 2-aryl substituent. Examinations of the microstructure of the elastomeric polypropylenes produced showed that for catalysts 2– 8 the isotacticities varied over a small range and were similar to those produced by catalyst 1 (20%≤[mmmm]≤44%). The catalyst productivities and molecular weights also showed the same trend. Complex 3 was crystallographically characterized and was found to crystallize in exclusively the meso conformation.

Ethylene polymerization with Cp2ZrCl2 supported on dealuminated Y zeolite

Y zeolites with different aluminium contents obtained by dealumination with ammonium hexafluorosilicate were evaluated as supports for bis(cyclopentadienyl)-zirconium dichloride catalysts. The activities of the supported and homogeneous systems were compared for ethylene polymerization. The most active heterogeneous catalyst was the one supported on the zeolite with the higher Si/Al ratio and external area.