Microstructure of polypropylene and active center in Ziegler–Natta catalyst: effect of novel salicylate internal donor

Zhou, Qian; Wang, Ailian; Li, Huayi; Luo, Zhi; Tao, Zheng; Zhang, Liaoyun; Hu, Youliang

doi:10.1039/c6ra13819e

Cited by 17 publications

(20 citation statements)

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“…Table 1. Salicylate donors (SID) with different substituent groups at R 1 , R 2 and R 3 positions and experimental data [16]. a %mm denotes the average meso (isotactic) sequence length or % triads of polypropylene from 13 C-NMR [16].…”

Section: Sidmentioning

confidence: 99%

“…b %I.I. denotes % of the isotactic index was tested by extraction with boiling n-heptane for 6 h [16].…”

Section: Sidmentioning

confidence: 99%

“…Their values in kcal/mol together with O-Mg distances in Å were listed in Table 2. The SID-4 was selected to represent the salicylate donor since this compound gave the highest activity in the experiment, see Table 1 [16]. Adsorption energies of the mono, the chelate, the bridge, and the zip coordination modes of the SID-4 adsorbed to the pre-activated MgCl 2 (110) surface are −30.2, −51.2 −45.9, and −42.0 kcal/mol, respectively.…”

Section: Preferred Adsorption Modes Of Salicylate Donorsmentioning

confidence: 99%

“…Table 1. Salicylate donors (SID) with different substituent groups at R1, R2 and R3 positions and experimental data [16].…”

Section: Introductionmentioning

confidence: 99%

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Roles of Salicylate Donors in Enhancement of Productivity and Isotacticity of Ziegler–Natta Catalyzed Propylene Polymerization

2020

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Roles of internal salicylate donors (SID) in enhancing activity and stereoselectivity of Ziegler–Natta catalyzed propylene (PP) polymerization were examined using DFT calculations. Five salicylate donors were studied. The chelate mode is the preferred adsorption mode. The linear relationship (R2 = 0.96) between calculated adsorption energies (Eads) of five SIDs and the experimental PP activities was observed. Thus, the SID with the strongest adsorption energy will provide the highest activity in agreement with our previous studies. Compared with diisobutyl phthalate (DIBP), which is the industrial electron donor, SID has stronger Eads. The insertion step, which involves the π-complex formation (∆Eπ) and the insertion activation or intrinsic activation energy (Ea) for PP polymerization was also examined. The relation between ln(activity) and apparent activation energy (Ea(app)), which is ∆Eπ + Ea for the primary(1,2)-re insertion with R2 = 0.99, was observed. The salicylate donor also has a lower Ea(app) than that of DIBP. This explains the better catalytic performance of SID. Our results also demonstrated that the size and the type of hydrocarbon substituents play a key role in controlling stereoselectivity and activity. In addition, we found a good relationship between Eads and both intrinsic (Ea) and apparent (Ea(app)) activation energies of five salicylate donors with R2 of 0.90 and 0.97, respectively.

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Section: Sidmentioning

confidence: 99%

“…b %I.I. denotes % of the isotactic index was tested by extraction with boiling n-heptane for 6 h [16].…”

Section: Sidmentioning

confidence: 99%

Section: Preferred Adsorption Modes Of Salicylate Donorsmentioning

confidence: 99%

“…Table 1. Salicylate donors (SID) with different substituent groups at R1, R2 and R3 positions and experimental data [16].…”

Section: Introductionmentioning

confidence: 99%

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Roles of Salicylate Donors in Enhancement of Productivity and Isotacticity of Ziegler–Natta Catalyzed Propylene Polymerization

2020

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“…), the diether‐containing catalysts can produce PP with lower molecular weight . In recent years, various new type of electron donors and mixtures of two De have been explored for developing ZN catalysts with improved preformances …”

Section: Introductionmentioning

confidence: 99%

Mechanism of internal and external electron donor effects on propylene polymerization with MgCl₂‐supported Ziegler–Natta catalyst: New evidences based on active center counting

Weng

Jiang

et al. 2018

J of Applied Polymer Sci

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Two TiCl 4 /Di/MgCl 2 type supported Ziegler-Natta catalysts were prepared by loading dibutylphthalate or dicyclopentyldimethoxysilane (DCPDMS) (internal donor, Di) and TiCl 4 on activated d-MgCl 2 in sequence, and a blank catalyst was prepared by loading TiCl 4 on the same d-MgCl 2 without adding Di. These catalysts have similar specific surface area and pore size distribution, thus form a suitable base for comparative studies. Propylene polymerization with the catalysts was conducted in n-heptane slurry using triethylaluminum (TEA) as cocatalyst, and the effects of Di as well as De (external donor, in this work it was DCPDMS) on the number of active centers, the distribution of active centers among three polypropylene (PP) fractions (isotactic, medium isotactic, and atactic PP chains), and chain propagation rate constants of the PP fractions were studied by counting the number of active centers in the PP fractions using a method based on selective quench-labeling of the propagation chains by 2-thiophenecarbonyl chloride. When De was not added in the polymerization, introducing a phthalate type Di in the catalyst evidently changed the active center distribution by enhancing the proportion of active centers producing isotactic PP (iPP) (C Ã i ), but scarcely changed reactivities of the three groups of active centers forming the three fractions. When the De was added in the polymerization system with TiCl 4 / phthalate/MgCl 2 catalyst, further shifting of active center distribution in favor of C Ã i took place, meanwhile reactivities of the three groups of active centers also remarkably changed in favor of C Ã i . Mutual effects of these changes led to overwhelming dominance of iPP production in the TiCl 4 /Di/MgCl 2 -TEA/De system (Di 5 phthalate, De 5 alkoxysilane). In contrast, though using alkoxysilane as Di also caused shifting of active center distribution in favor of C Ã i when De was not added, addition of alkoxysilane De caused reverse shifting of active center distribution in favor of those producing PP of lower stereoregularity. This unfavorable change largely counteracted the reactivity changes in favor of C Ã i caused by the De, rendering the catalytic system rather poor isospecificity. V C 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46605.

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Ziegler–Natta Catalysts

Fan

2018

Encyclopedia of Polymer Science and Technology

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First invented in 1953, Ziegler–Natta catalysts have been used widely in the industrial production of polyolefins and other important polymers since the 1960s. In recent years, polymers synthesized with these catalysts account for more than 30% of the total production of polymers. This article briefly introduces the history and main developments of Ziegler–Natta catalysts and explains their preparation, composition, and mechanism of the catalysis process. Particular emphasis is put on the currently more important MgCl 2 ‐supported Ziegler–Natta catalysts. Main features of the olefin polymerization with MgCl 2 ‐supported Ziegler–Natta catalysts are presented, including the formation and structure of active sites, main reactions with the active sites, origin of stereospecificity, reaction kinetics, and morphology of the nascent polymer particles. The main olefin polymerization processes with these catalysts are also briefly discussed.

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Microstructure of polypropylene and active center in Ziegler–Natta catalyst: effect of novel salicylate internal donor

Abstract: The volume of ecofriendly salicylate internal donors for propylene polymerization has an important impact on the catalyst active centers and microstructure of polypropylene.

Cited by 17 publications

References 35 publications

Roles of Salicylate Donors in Enhancement of Productivity and Isotacticity of Ziegler–Natta Catalyzed Propylene Polymerization

Roles of Salicylate Donors in Enhancement of Productivity and Isotacticity of Ziegler–Natta Catalyzed Propylene Polymerization

Mechanism of internal and external electron donor effects on propylene polymerization with MgCl₂‐supported Ziegler–Natta catalyst: New evidences based on active center counting

Ziegler–Natta Catalysts

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Microstructure of polypropylene and active center in Ziegler–Natta catalyst: effect of novel salicylate internal donor

Abstract: The volume of ecofriendly salicylate internal donors for propylene polymerization has an important impact on the catalyst active centers and microstructure of polypropylene.

Cited by 17 publications

References 35 publications

Roles of Salicylate Donors in Enhancement of Productivity and Isotacticity of Ziegler–Natta Catalyzed Propylene Polymerization

Roles of Salicylate Donors in Enhancement of Productivity and Isotacticity of Ziegler–Natta Catalyzed Propylene Polymerization

Mechanism of internal and external electron donor effects on propylene polymerization with MgCl2‐supported Ziegler–Natta catalyst: New evidences based on active center counting

Ziegler–Natta Catalysts

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Mechanism of internal and external electron donor effects on propylene polymerization with MgCl₂‐supported Ziegler–Natta catalyst: New evidences based on active center counting