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Journal articles on the topic 'Metallocene Catalyst'

Author: Grafiati

Published: 4 June 2021

Last updated: 8 February 2022

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1

Yang, Qing, and Max Paul McDaniel. "Comparison of Support Effects on Phillips and Metallocene Catalysts." Catalysts 11, no. 7 (July 13, 2021): 842. http://dx.doi.org/10.3390/catal11070842.

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Both metallocene and Phillips chromium catalysts are used in the commercial manufacture of polyethylene. Unlike most other commercial metallocene systems, the Chevron Phillips Chemical (CPC) platform does not use methylaluminoxane or fluoroorganic boranes. Instead, the support itself serves to activate (ionize) the metallocenes, which then polymerize ethylene at high activity. Most of these solid acid supports can also be used to anchor Cr to make a Phillips catalyst. This provides an interesting opportunity to compare the polymerization responses by these two disparate systems, Phillips Cr and CPC metallocene, when supported on the same solid acid carriers. In this study, both chromium oxide and several metallocenes were deposited onto a variety of solid oxides, under a variety of conditions, and the resulting support effects were observed and compared. Although using seemingly different chemistries, the two catalyst systems exhibited a surprising number of similarities, which can be attributed to the acidity and porosity of these diverse supports.

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2

Zhou, Wei, Lei Zhong, and Wei Dong Li. "Progress in Development of Catalyst Systems for Coordinated Polymerization of Olefins." Advanced Materials Research 900 (February 2014): 11–14. http://dx.doi.org/10.4028/www.scientific.net/amr.900.11.

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The research progresses about polyolefin catalyst systems in recent years are summarized. Focusing on the type and properties of the catalytic polymerization of the olefin polymerization catalyst, including typical Ziegler-Natta catalysts, metallocene catalysts and post-transition metal catalyst system. Then the new post-transition metal catalyst is introduced.

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3

Moncada, E., R. Quijada, and P. Zapata. "Modification of Clays by Sol-Gel Reaction and Their Use in the EthyleneIn SituPolymerization for Obtaining Nanocomposites." Journal of Nanomaterials 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/348156.

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The nanocomposites formation byin situpolymerization used a metallocene catalyst (butyl-2-cyclopentadienyl zirconium 2-chlorines) and a hectorite synthetic clay type which is discussed. This research was carried out in two phases. The first phase consisted of mixing the components of the metallocenic polymerization reaction (metallocene-methylaluminoxane-ethylene) with clay in a reactor. In the second phase, the metallocenic catalytic system was supported by clay particles and then a polymerization reaction was made. In this second phase, the clay particles were modified using a sol-gel reaction with different pH values: pH = 3, pH = 8, and pH = 12. The results were compared in terms of the catalytic activity in the different systems (phase 1 and phase 2) and the nanoparticle morphology of nanocomposites generated in this study.

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4

Baek, Jun Won, Su Jin Kwon, Hyun Ju Lee, Tae Jin Kim, Ji Yeon Ryu, Junseong Lee, Eun Ji Shin, Ki Soo Lee, and Bun Yeoul Lee. "Preparation of Half- and Post-Metallocene Hafnium Complexes with Tetrahydroquinoline and Tetrahydrophenanthroline Frameworks for Olefin Polymerization." Polymers 11, no. 7 (June 27, 2019): 1093. http://dx.doi.org/10.3390/polym11071093.

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Hafnium complexes have drawn attention for their application as post-metallocene catalysts with unique performance in olefin polymerization. In this work, a series of half-metallocene HfMe2 complexes, bearing a tetrahydroquinoline framework, as well as a series of [Namido,N,Caryl]HfMe2-type post-metallocene complexes, bearing a tetrahydrophenanthroline framework, were prepared; the structures of the prepared Hf complexes were unambiguously confirmed by X-ray crystallography. When the prepared complexes were reacted with anhydrous [(C18H37)2N(H)Me]+[B(C6F5)4]−, desired ion-pair complexes, in which (C18H37)2NMe coordinated to the Hf center, were cleanly afforded. The activated complexes generated from the half-metallocene complexes were inactive for the copolymerization of ethylene/propylene, while those generated from post-metallocene complexes were active. Complex bearing bulky isopropyl substituents (12) exhibited the highest activity. However, the activity was approximately half that of the prototype pyridylamido-Hf Dow catalyst. The comonomer incorporation capability was also inferior to that of the pyridylamido-Hf Dow catalyst. However, 12 performed well in the coordinative chain transfer polymerization performed in the presence of (octyl)2Zn, converting all the fed (octyl)2Zn to (polyolefinyl)2Zn with controlled lengths of the polyolefinyl chain.

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5

Marques, Maria, and Rodrigo Tiosso. "Brazilian Mineral Clay as Support for Metallocene Catalyst in the Synthesis of Polyethylene." Chemistry and Chemical Technology 4, no. 2 (June 15, 2010): 139–46. http://dx.doi.org/10.23939/chcht04.02.139.

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Silica was compared with clays as supports for metallocene. Ethylene homopolymerization with both homogeneous and heterogeneous catalysts was performed. Activation energy was higher for (n-BuCp)2ZrCl2/SiO2/MAO, although high activities were obtained for catalysts with clay. They showed Ea close to that of homogeneous precursor. Catalyst/clay control polymer morphology until 363 K

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6

Chien, James C. W., and Dawei He. "Olefin copolymerization with metallocene catalysts. III. Supported metallocene/methylaluminoxane catalyst for olefin copolymerization." Journal of Polymer Science Part A: Polymer Chemistry 29, no. 11 (October 1991): 1603–7. http://dx.doi.org/10.1002/pola.1991.080291109.

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7

van Reenen, Albert J., and Omar Sultan. "The Effect of Catalyst Isomerization on Polypropylene Properties." Zeitschrift für Naturforschung B 62, no. 3 (March 1, 2007): 362–66. http://dx.doi.org/10.1515/znb-2007-0309.

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Two C2-symmetric metallocene catalysts in solution were exposed to light, and the rac-meso conversion followed by NMR spectroscopy. Both exposed and unexposed catalyst solutions were used, in conjunction with a suitable cocatalyst, to polymerize propylene. The polymers were characterized with respect to their microstructure and fractionated according to crystallinity. The relationship between the catalyst isomerization and the polymer structure is illustrated. The effect of pre-activation of the catalyst before exposure to light was also studied and is reported on.

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8

Vieira Marques, Maria de Fátima, Fernanda Constantino Rocha, and Narda Juárez Soto. "Copolymerization of Ethylene/Diene with Different Metallocene Catalysts." Zeitschrift für Naturforschung B 61, no. 11 (November 1, 2006): 1426–32. http://dx.doi.org/10.1515/znb-2006-1117.

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Copolymerizations of ethylene and 1,7-octadiene were carried out employing homogeneous catalysts Cp2ZrCl2, Ph2C(Flu,Cp)ZrCl2 and Et(Ind)2ZrCl2, and methylaluminoxane as cocatalyst. The polymerization characteristics, such as catalytic activity, polymerization rate, copolymer composition, and thermal properties were examined in relation to the catalyst type. Different comonomer concentrations were employed, and the reaction time was varied, ranging from 1 h up to 4 h, at 90°C and at 0.5 bar ethylene pressure. The results showed that the catalyst Cp2ZrCl2 was more efficient than Et(Ind)2ZrCl2 in the preparation of high diene content ethylene/1,7-octadiene copolymers. On the other hand, Et(Ind)2ZrCl2 and Ph2C(Flu,Cp)2ZrCl2 catalysts produced low insaturation content but possibly formed cyclic structures and crosslinking.

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9

Nguyen, Thanh Thi Le, and Nhon Thi Le Nguyen. "Synthesis of polystyrene-block-poly(iso-butyl vinyl ether) by dinuclear half-metallocene catalyst and atom transfer radical polymerization." Science and Technology Development Journal 18, no. 3 (August 30, 2015): 189–99. http://dx.doi.org/10.32508/stdj.v18i3.835.

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The synthesis of polystyrene-block-poly(iso-butyl vinyl ether) by using the combination of metallocene catalyst and atom transfer radical polymerization (ATRP) has been tried. This synthetic method takes advantages of both metallocene catalyst to form stereoregular polymer with high activity and ATRP with the controlled molecular weights and low polydispersity. The recent dinuclear half-sandwich complexes of titanium with xylene bridge, [Ti(η5-cyclopentadienyl)Cl2L]2-ortho, meta-[CH2-C6H4-CH2] (L = Cl, L = O-2,6-iPr2C6H3 ) were successfully synthesized. These catalysts were characterized by 1H NMR, 13C NMR and elemental analysis. Copolymers have been characterized by using gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR). The collected copolymers have got narrow molecular weight distribution (≤1.8) and the improvement of stereoregularity (racemo dyads, r, are from 45 % to 56 %).

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10

Turner, Howard W. "5599761 Ionic metallocene catalyst compositions." Journal of Molecular Catalysis A: Chemical 125, no. 2-3 (November 1997): 164. http://dx.doi.org/10.1016/s1381-1169(98)80055-1.

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11

Nele, Marcio, Muqtar Mohammed, Shixuan Xin, Scott Collins, Marcos L. Dias, and J. C. Pinto. "Two-State Models for Propylene Polymerization Using Metallocene Catalysts. 2. Application toansa-Metallocene Catalyst Systems." Macromolecules 34, no. 12 (June 2001): 3830–41. http://dx.doi.org/10.1021/ma0021186.

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12

Schloegla, Martin, Carsten Trolla, Ulf Thewaltb, and Bernhard Riegera. "Semi-Hydrogenated, Asymmetric Metallocene Catalysts for the Propylene Polymerization." Zeitschrift für Naturforschung B 58, no. 6 (June 1, 2003): 533–38. http://dx.doi.org/10.1515/znb-2003-0608.

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The hydrogenation of rac-[1-(9-η5-fluorenyl)-2-(5,6-cylopenta-2-methyl-1-η5-indenyl)ethane] metallocene dichlorides (1a: Zr, 1b: Hf) with PtO2/H2O/H2 is reported. The diastereoselective formation of exclusively rac-[1-(2,3,4,5,6,7,8,9-octahydro-η5-fluorenyl)-2-(2-methyl- 1,4,4a(R;S),5,6,7,7a(S;R),8-octahydro-s-η5-indacenyl)ethane]metallocene dichlorides (2a: Zr, 2b: Hf) was shown by 1H-NMR and by X-ray analysis of 2a. Both compounds were activated in situ with triisobutylaluminum/PhC+3 [B(C6F5)4]D and tested as catalysts in propylene polymerization reactions. Comparison to the non-hydrogenated complexes revealed a decrease in molecular weight of the polymer and in catalyst activity. Experiments at elevated temperatures resulted in a lower stereospecificity and reduced isotacticity values indicating a polymerization mechanism analogous to C2-symmetric catalysts.

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13

KIRSCHNER, ELISABETH. "Phillips develops LLDPE metallocene catalyst system." Chemical & Engineering News 75, no. 10 (March 10, 1997): 12. http://dx.doi.org/10.1021/cen-v075n010.p012.

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14

Steinmetz, B., B. Weimann, G. Fink, and B. Tesche. "SIO2-Supported Metallocene Catalysts for Propene Polymerization: Electron Microscopic Studies and Tomographical Reconstructions of Polymer Growth." Microscopy and Microanalysis 6, S2 (August 2000): 1126–27. http://dx.doi.org/10.1017/s1431927600038125.

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Summary:The polypropylene growth process on silica supported metallocene catalysts was examined by electron microscopy and kinetic investigations. It was possible to identify different polymerization stages with different characteristic kinetic data in the slurry phase which led to the development of a refined polymer growth model [1-2]. Tomographical reconstruction of shortly polymerized catalyst particles obtained by electron micrographs of serial microtome sections turned out to be a useful tool to achieve a better understanding of the heterogeneous polymerization process and the influence of the support structure on polymer growth.1. IntroductionSingle-site metallocene catalysts produce extremely uniform polymers with molecular weight distributions (MWD) of 2 or less and very narrow compositional distributions in comparison to conventional Ziegler-catalysts. For industrial gas phase or bulk polymerization in existing plants (drop-in-technology) it is necessary to fix the catalytically active components on a heterogeneous support.

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15

Nele, Márcio, Scott Collins, M. L. Dias, J. C. Pinto, Shirley Lin, and Robert M. Waymouth. "Two-State Models for Olefin Polymerization using Metallocene Catalysts. 1. Application to Fluxional Metallocene Catalyst Systems." Macromolecules 33, no. 20 (October 2000): 7249–60. http://dx.doi.org/10.1021/ma000401z.

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16

Spaleck, Walter, Michael Aulbach, Bernd Bachmann, Frank Küber, and Andreas Winter. "Stereospecific metallocene catalysts: Scope and limits of rational catalyst design." Macromolecular Symposia 89, no. 1 (January 1995): 237–47. http://dx.doi.org/10.1002/masy.19950890124.

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17

Tumawong, Praonapa, Ekrachan Chaichana, and Bunjerd Jongsomjit. "Effect of Immobilization Methods on the Production of Polyethylene-cellulose Biocomposites via Ethylene Polymerization with Metallocene/MAO Catalyst." Bulletin of Chemical Reaction Engineering & Catalysis 15, no. 3 (October 3, 2020): 752–64. http://dx.doi.org/10.9767/bcrec.15.3.8735.752-764.

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Polyethylene-cellulose biocomposites were synthesized here via the ethylene polymerization with metallocene as a catalyst along with methylaluminoxane (MAO) as a cocatalyst. The immobilization method in which the catalyst or cocatalyst is fixed onto the catalytic filler (cellulose) can be classified into 3 methods according to the active components fixed onto the filler surface: 1) only metallocene catalyst (Cellulose/Zr), 2) only MAO cocatalyst (Cellulose/MAO) and 3) mixture of metallocene and MAO (Cellulose/(Zr+MAO)). It was found that the different immobilization methods or different fillers altered the properties of the obtained composites and also the catalytic activity of the polymerization systems. It was found that Cellulose/MAO provided the highest catalytic activity among all fillers due to a crown-alumoxane complex, which caused the heterogeneous system with this filler behaved similarly to the homogeneous system. The different fillers also produced the biocomposites with some different properties such as crystallinity which Cellulose/Zr provided the highest crystallinity compared with other fillers as observed by a thermal gravimetric analysis-differential scanning calorimetry (TGA-DSC). Nevertheless, the main crystal structure indicated to the typical polyethylene was still observed for all obtained biocomposites with different fillers as observed by an X-ray diffractometer (XRD). Copyright © 2020 BCREC Group. All rights reserved

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18

Wang, Qiliao, Shanshan Chen, Bicheng Deng, Ying Wang, Dewen Dong, and Ning Zhang. "Rare earth metal-mediated ring-opening polymerisation of cyclic phosphoesters." Polymer Chemistry 10, no. 17 (2019): 2101–5. http://dx.doi.org/10.1039/c9py00025a.

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19

Buffet, Jean-Charles, Zoë R. Turner, Robert T. Cooper, and Dermot O'Hare. "Ethylene polymerisation using solid catalysts based on layered double hydroxides." Polymer Chemistry 6, no. 13 (2015): 2493–503. http://dx.doi.org/10.1039/c4py01742k.

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We report here the use of methylaluminoxane (MAO) modified aqueous miscible organic solvent treated (AMOST) layered double hydroxide, Mg₆Al₂(OH)₁₆CO₃·4H₂O (AMO-Mg₃Al-CO₃) as a catalyst support system for the slurry phase polymerisation of ethylene using immobilised metallocene and non-metallocene metal complexes.

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20

Ewen, John, and Michael Elder. "5614457 Catalyst system using aluminum alkyl with ion-pair metallocene catalysts." Journal of Molecular Catalysis A: Chemical 125, no. 2-3 (November 1997): 170. http://dx.doi.org/10.1016/s1381-1169(98)80073-3.

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21

Siedle, A. R., Kristin M. Theissen, and John Stevens. "A measure of metallocene catalyst shape asymmetry." Journal of Molecular Catalysis A: Chemical 191, no. 2 (January 2003): 167–75. http://dx.doi.org/10.1016/s1381-1169(02)00245-5.

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22

Aaltonen, Päivi, and Barbro Löfgren. "Functionalization of polyethylenes via metallocene/methylaluminoxane catalyst." European Polymer Journal 33, no. 8 (August 1997): 1187–90. http://dx.doi.org/10.1016/s0014-3057(97)00011-6.

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23

Marques, Maria de Fátima V., Carla C. Pombo, Rodrigo A. Silva, and Anunciata Conte. "Binary metallocene supported catalyst for propylene polymerization." European Polymer Journal 39, no. 3 (March 2003): 561–67. http://dx.doi.org/10.1016/s0014-3057(02)00269-0.

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24

ASANUMA, TADASHI. "Preparation of New Polyolefins using Metallocene Catalyst." NIPPON GOMU KYOKAISHI 69, no. 3 (1996): 161–70. http://dx.doi.org/10.2324/gomu.69.161.

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25

Götz, Christian, Alexander Rau, and Gerhard Luft. "Investigations on ternary metallocene-based catalyst systems." Macromolecular Symposia 178, no. 1 (February 2002): 93–108. http://dx.doi.org/10.1002/1521-3900(200202)178:1<93::aid-masy93>3.0.co;2-l.

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26

Shiomura, Tetsunosuke, Tadashi Asanuma, and Norihide Inoue. "Inversion of stereoselectivity in a metallocene catalyst." Macromolecular Rapid Communications 17, no. 1 (January 1996): 9–14. http://dx.doi.org/10.1002/marc.1996.030170102.

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27

Mileva, Daniela, Jingbo Wang, René Androsch, Katalee Jariyavidyanont, Markus Gahleitner, and Klaus Bernreitner. "Crystallization of Random Metallocene-Catalyzed Propylene-Based Copolymers with Ethylene and 1-Hexene on Rapid Cooling." Polymers 13, no. 13 (June 25, 2021): 2091. http://dx.doi.org/10.3390/polym13132091.

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Propylene-based random copolymers with either ethylene or 1-hexene as comonomer, produced using a metallocene catalyst, were studied regarding their crystallization behaviors, with a focus on rapid cooling. To get an impression of processing effects, fast scanning chip calorimetry (FSC) was used in addition to the characterization of the mechanical performance. When comparing the comonomer type and the relation to commercial grades based on Ziegler–Natta-type catalysts, both an interaction with the catalyst-related regio-defects and a significant difference between ethylene and 1-hexene was observed. A soluble-type nucleating agent was found to modify the behavior, but to an increasingly lesser degree at high cooling rates.

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28

Walton, Kim L., Morgan M. Hughes, and Deepak R. Parikh. "A New Class of Ethylene—Propylene—Diene Terpolymers Produced from Constrained Geometry Metallocene Catalysts." Rubber Chemistry and Technology 74, no. 4 (September 1, 2001): 688–700. http://dx.doi.org/10.5254/1.3544967.

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Abstract Until recently, ethylene/propylene/diene (EPDM) terpolymers have been manufactured exclusively using vanadium based Ziegler—Natta catalyst systems. The vanadium based catalysts are known to have both product and process limitations. These limitations are due to a complex combination of factors including monomer reactivity, catalyst activity, reactor temperatures and pressures. Single-site metallocene constrained geometry catalyst (CGC) technology enables the manufacture of EPDM terpolymers at higher reactor temperature and catalyst efficiency than standard Ziegler—Natta catalyst systems. The unique combination of monomer, catalyst and process technology enables the manufacture of highly crystalline EPDMs having ethylene contents over 90 wt %. This study investigated these new highly crystalline EPDM terpolymers and their differentiation from commercially available EPDMs. The results indicated that these new EPDMs had very high green strength and barrier properties, yet could be cured by conventional vulcanization techniques. The cure response of these EPDMs to either peroxide or sulfur increased with increasing ethylene content. Sulfur cured vulcanizates had much higher tensile strength than peroxide cured vulcanizates. These new EPDMs demonstrated utility as additives to enhance the abrasion, hot tear, and tensile properties of natural rubber compounds. Sponge compounds, having the unique combination of polyethylene physical properties and the utility of sulfur vulcanization were developed from these new polymers.

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29

Chung, T. C., H. L. Lu, and S. Hong. "New Polyolefin Elastomers Containing “Reactive” p-Methylstyrene Units: Preparation by Metallocene Catalysts." Rubber Chemistry and Technology 72, no. 2 (May 1, 1999): 283–98. http://dx.doi.org/10.5254/1.3538801.

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Abstract This paper summarizes the experimental results of three new polyolefin elastomers, i.e., poly(1-octene-co- p-methylstyrene (O-p-MS), poly(ethylene-ter-propylene-ter-p-methylstyrene) (EP-p-MS) and poly(ethylene-ter-1-octene-ter-p-methylstyrene) (EO-p-MS), containing “reactive” p-MS units. Both Ziegler-Natta and metallocene catalysts were used in studying co- and ter-polymerization reactions. In the copolymerization of 1-octene and p-MS, Ziegler-Natta catalyst TiCl3/AlEt3 exhibits higher catalyst reactivity to produce high molecular weight O-p-MS copolymers, containing up to 20 mol % p-MS. However, the copolymers show very broad composition and molecular weight distributions. On the other hand, two EP-p-MS and EO-p-MS terpolymers with narrow molecular weight and composition distributions were prepared by [C5Me4(SiMe2NtBu)]TiCl2 metallocene catalyst with constrained ligand geometry. The sharp glass transition temperature (Tg) with flat baseline in each differential scanning calorimetry (DSC) curve indicates homogeneous terpolymer microstructures. The Tg of EP-p-MS is very sensitive to the terpolymer composition (ethylene/propylene ratio and p-MS content). In the compositions with ideal ethylene/propylene ratio ∼ 55/45, the Tα is almost proportional to the content of p-MS. Only with the concentration of p-MS < 2 mol %, does the EP-p-MS show alow Tg<−45°C. On the other hand, the EO-p-MS system exhibits a low Tg<−50°C in a wide range of copolymer compositions, even ones with relatively high p-MS contents (< 7 mol %).

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30

Wang, Jing, Xiao Yan Liu, Jun Ji Jia, Xu Chen, and Bo Chao Zhu. "Study of Ziegler-Natta /Metallocene Hybrid Catalyst on Pilot Device." Advanced Materials Research 396-398 (November 2011): 8–12. http://dx.doi.org/10.4028/www.scientific.net/amr.396-398.8.

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In this work, Ziegler-Natta/Metallocene hybrid catalyst (Z-M) was prepared magnifying. The activity and copolymerization behavior of the catalyst were evaluated through 10L model device. Model experiment results confirmed that the catalyst was suitable for Spheripol-II PP pilot device. Subsequently, pilot experiment was carried out on 75 kgPP/h Spheripol-II PP pilot device. SP179 which was prepared by traditional Ziegler-Natta catalyst was used as a reference object. Pilot experiment results showed that: Z-M hybrid catalyst demonstrated good activity and copolymerization properties. The resultant polypropylene in-reactor alloys have better impact strength and flowability than SP179. These alloys showed good stiffness-toughness balance. The impact strength and the flexural modulus of the best alloy was 50 kJ/m2 at 23 °C and 848 MPa, respectively. The other performances were similar to that of SP179. But Z-M hybrid catalyst required lower feed ratio of ethylene than the traditional Ziegler-Natta catalyst for SP179.

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31

Brown, Steve J., Xiaoliang Gao, Matthew G. Kowalchuk, Rupert E. v. H. Spence, Douglas W. Stephan, and John Swabey. "Synthesis and characterization of titanium complexes containing phosphinimido and tropidinyl ligands: Crystal structure of (trop)(t-Bu3PN)TiCl2." Canadian Journal of Chemistry 80, no. 11 (November 1, 2002): 1618–24. http://dx.doi.org/10.1139/v02-170.

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A new class of titanium complexes containing a tropidinyl (trop) ligand and a phosphinimido (R3P=N-) or a ketimide ligand (R2C=N-) were synthesized and characterized. The combination of the cyclopentadienyl equivalent tropidinyl and phosphinimido ligands enables the formation of a group of novel non-metallocene catalysts for olefin polymerization. The crystal structure of (trop)(t-Bu3PN)TiCl2 was determined by single crystal X-ray crystallography. Polymerization of ethylene with this complex was studied in a high-temperature solution process.Key words: tropidinyl, phosphinimido, ketimide, catalyst, polymerization.

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32

Geng, Jieting, Youguo Shao, Feng Song, Feng Li, and Jing Hua. "Binary molybdenum-based catalyst for coordination polymerization of styrene." Journal of Elastomers & Plastics 49, no. 5 (September 27, 2016): 408–21. http://dx.doi.org/10.1177/0095244316668930.

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Coordination polymerization of styrene (St) using molybdenum pentachloride supported by phosphite ligand in the presence of metal organic compound was studied for the first time. The types of phosphite and co-catalysts significantly affected the catalytic activity of the molybdenum (V) (Mo(V)) active center and the number-average molecular weight ( Mn) of the resultant polymer. Among the examined catalysts, tri(nonylphenyl)phosphite (TNPP) ligand and AlOPhCH3( i-Bu)2 as co-catalyst provided the polymer with highest yield (up to 87.1%), metallocene as co-catalyst provided the polymer with highest Mn (up to 5.32 × 105). The effect of [P]/[Mo] molar ratio on catalyst activity of the polymerization was discussed and the structures of Mo·TNPP complexes were preliminarily studied by infrared (IR) and ultraviolet spectroscopies. Besides, the polystyrene (PS) samples synthesized through bulk polymerization and solution polymerization were characterized by gel permeation chromatography, IR, carbon 13 nuclear magnetic resonance, and differential scanning calorimetry, respectively, and the results indicated both of the PS had high molecular weight (approximately 105) and atactic structure. All these results demonstrated that Mo(V) catalyst system was very effective for St polymerization.

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33

Götz, Christian, Alexander Rau, and Gerhard Luft. "Ternary metallocene catalyst systems based on metallocene dichlorides and AlBu3i/[PhNMe2H][B(C6F5)4]." Journal of Molecular Catalysis A: Chemical 184, no. 1-2 (June 2002): 95–110. http://dx.doi.org/10.1016/s1381-1169(01)00517-9.

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34

Buffet, Jean-Charles, Zoë R. Turner, and Dermot O’Hare. "Popcorn-shaped polyethylene synthesised using highly active supported permethylindenyl metallocene catalyst systems." Chemical Communications 54, no. 78 (2018): 10970–73. http://dx.doi.org/10.1039/c8cc05350b.

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Unsymmetrical permethylindenyl bent metallocene complexes have been synthesised and reacted with inorganic solid supports to afford highly active catalysts for the slurry phase polymerisation of ethylene with desirable, low aggregation, “popcorn” morphology.

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35

Yasin, Tariq, Zhiqiang Fan, and Linxian Feng. "Synthesis of unbridged metallocene catalyst for propylene polymerization." European Polymer Journal 40, no. 3 (March 2004): 517–22. http://dx.doi.org/10.1016/j.eurpolymj.2003.10.022.

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36

Reddy, S. "Homogeneous metallocene-methylaluminoxane catalyst systems for ethylene polymerization." Progress in Polymer Science 20, no. 2 (1995): 309–67. http://dx.doi.org/10.1016/0079-6700(94)00035-z.

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37

Kitagawa, Takeshi, Toshiya Uozumi, Kazuo Soga, and Toshikazu Takata. "Syndiospecific propene polymerization with polymer-supported metallocene catalyst." Polymer 38, no. 3 (February 1997): 615–20. http://dx.doi.org/10.1016/s0032-3861(96)00535-6.

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38

Nguyen, Huy V., David C. D. Butler, and Christopher J. Richards. "A Metallocene-Pyrrolidinopyridine Nucleophilic Catalyst for Asymmetric Synthesis." Organic Letters 8, no. 4 (February 2006): 769–72. http://dx.doi.org/10.1021/ol053050n.

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39

van Grieken, Rafael, Carlos Martín, Jovita Moreno, Oscar Prieto, and Jose M. Bravo. "Ethylene/1-Butene Copolymerization over Heterogeneous Metallocene Catalyst." Macromolecular Symposia 259, no. 1 (December 2007): 174–80. http://dx.doi.org/10.1002/masy.200751320.

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40

Leclerc, Margarete K., and Robert M. Waymouth. "Alternating Ethene/Propene Copolymerization with a Metallocene Catalyst." Angewandte Chemie International Edition 37, no. 7 (April 20, 1998): 922–25. http://dx.doi.org/10.1002/(sici)1521-3773(19980420)37:7<922::aid-anie922>3.0.co;2-g.

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41

Ahmadi, Mostafa, Roghieh Jamjah, Mehdi Nekoomanesh, Gholam Hossein Zohuri, and Hassan Arabi. "Ziegler-Natta/Metallocene Hybrid Catalyst for Ethylene Polymerization." Macromolecular Reaction Engineering 1, no. 6 (November 20, 2007): 604–10. http://dx.doi.org/10.1002/mren.200700027.

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42

de Fátima Vieira Marques, Maria, Carla Camargo Pombo, Rodrigo Azevedo Silva, and Anunciata Conte. "Supported stereospecific metallocene binary catalyst for propylene polymerization." Journal of Polymer Science Part A: Polymer Chemistry 40, no. 17 (July 17, 2002): 2979–86. http://dx.doi.org/10.1002/pola.10380.

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43

Wang, Wei, Liping Hou, and Jianfang Sheng. "Syndiotactic Polymer of Allylcyclopentane by a Metallocene Catalyst." ChemCatChem 8, no. 20 (September 14, 2016): 3218–23. http://dx.doi.org/10.1002/cctc.201600711.

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44

Zhou, Annan, Yuejuan Zhang, Yasai Shi, and Qinghong Xu. "Integrated synthesis of metallocene@support catalysts based on glyphosate and its zirconium derivatives." RSC Advances 7, no. 88 (2017): 55866–73. http://dx.doi.org/10.1039/c7ra11089h.

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Three new kinds of composite metallocene catalyst, Cp₂Zr@Gly, Cp₂Zr@ZrGp and Cp₂Zr@EXZrGP, were synthesized and their catalytic activity in ethylene polymerization was studied.

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45

Erker, Gerhard, Christian Psiorz, and Roland Fröhlich. "A Rigid C1-Bridged Ansa-Zirconocene-Derived Catalyst System Suited for Stereoselective Low Molecular Weight Polypropylene Formation." Zeitschrift für Naturforschung B 50, no. 4 (April 1, 1995): 469–75. http://dx.doi.org/10.1515/znb-1995-0403.

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2,5-Hexanedione was converted into the bisfulvene 2, then treated with two molar equivalents of methyllithium to yield the [4-cyclopentadienylidene-4,7,7-trimethyl-4,5,6,7-tetrahydroindenyl] dilithio compound 4. Hydrolysis, followed by treatment with acetone/pyrrolidine, gave the corresponding fulvene system 5. Reaction of 5 with methyllithium followed by treatment with ZrCl4 furnished the ring-annulated C1-bridged ansa-metallocene 8, bearing a tert-butyl substituent at the Cp ring, as a 1:1 mixture of two diastereoisomers. Treatment of the fulvene 5 with LiAlH4 followed by ZrCl4 yielded the respective isopropyl-substituted ansa-metallocene diastereomers 9a and 9b. Complex 9b was separated by fractional crystallization and characterized by X-ray diffraction. Complexes 8 and 9 provide active homogeneous Ziegler-type catalyst systems upon activation with excess methylalumoxane producing low molecular weight isotactic polypropylene with high catalyst activities.

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46

Bai, Fu Chen, Chun Xiao Zhang, Xi Yao Zhang, Jian Liu, and Wei Tian. "Photo-Oxidative Degradation of Metallocene Linear Low-Density Polyethylene." Materials Science Forum 610-613 (January 2009): 243–47. http://dx.doi.org/10.4028/www.scientific.net/msf.610-613.243.

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Films of linear-low density polyethylenes, made from metallocene catalyst and Ziegler-Natta catalyst , were exposed to accelerate photo-oxidation conditions. The investigations were focused on the changes of the physical and chemical structures and elongation at break occurring in the photo-oxidation process. The results showed that ethylene-hexene m-LLDPE was more favorer to photo-oxidize than ethylene-octene LLDPE. The other two ethylene-ocetene m-LLDPEs were comparable to LLDPE with the same comonomer. The oxidation rate of LDPE is slower than those of all the LLDPEs.

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Marques, Maria de Fátima V., Daniela E. B. Lopes, Juliana B. Brandão, and Cristiane A. Henriques. "Polyethylene Synthesis Catalyzed By Cp2ZrCl2 Supported On Mordenites With Different Physico-Chemical Properties." Zeitschrift für Naturforschung B 60, no. 3 (March 1, 2005): 312–17. http://dx.doi.org/10.1515/znb-2005-0313.

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The commercial zeolite sodic mordenite was chemically and thermally treated in order to obtain materials with different physico-chemical properties to be employed as support for the metallocene bis(cyclopentadienyl)zirconium dichloride used for ethylene polymerization. The supports obtained were characterized regarding their chemical composition, textural properties as well as Lewis and Brφnsted sites concentrations. It was verified that the original zeolite without dealumination treatment was the most active catalyst followed by the material dealuminated with steam. All the supported catalysts produced polyethylene with higher molecular weight in relation to that obtained with the homogeneous counterpart

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48

Vittoria, Antonio, Georgy P. Goryunov, Vyatcheslav V. Izmer, Dmitry S. Kononovich, Oleg V. Samsonov, Francesco Zaccaria, Gaia Urciuoli, et al. "Hafnium vs. Zirconium, the Perpetual Battle for Supremacy in Catalytic Olefin Polymerization: A Simple Matter of Electrophilicity?" Polymers 13, no. 16 (August 6, 2021): 2621. http://dx.doi.org/10.3390/polym13162621.

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The performance of C2-symmetric ansa-hafnocene catalysts for isotactic polypropylene typically deteriorates at increasing temperature much faster than that of their zirconium analogues. Herein, we analyze in detail a set of five Hf/Zr metallocene pairs—including some of the latest generation catalysts—at medium- to high-polymerization temperature. Quantitative structure–activity relationship (QSAR) models for stereoselectivity, the ratio allyl/vinyl chain ends, and 2,1/3,1 misinsertions in the polymer indicate a strong dependence of polymerization performance on electrophilicity of the catalyst, which is a function of the ligand framework and the metal center. Based on this insight, the stronger performance decline of hafnocenes is ascribed to electrophilicity-dependent stabilization effects.

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Zhang, Zhongyue, Xiaofang Duan, Ying Zheng, Jingzun Wang, Guangzhong Tu, and Shaoliang Hong. "In situ1H- and27AL-NMR studies on metallocene catalyst systems?Catalysts for olefin polymerization." Journal of Applied Polymer Science 77, no. 4 (July 25, 2000): 890–97. http://dx.doi.org/10.1002/(sici)1097-4628(20000725)77:4<890::aid-app24>3.0.co;2-y.

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Chen, Zhikang, Yuanhong Mao, Yucai Cao, Shengbiao Liang, Sha Song, Chen Ni, Zhenyu Liu, Xiaofeng Ye, An Shen, and Hongping Zhu. "Metallocene Catalyst Systems and Control over the Propylene Polymerization." Chinese Journal of Organic Chemistry 38, no. 11 (2018): 2937. http://dx.doi.org/10.6023/cjoc201803047.

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