Kinetics and mechanism of ethylene and propylene polymerizations catalyzed with ansa-zirconocene activated by borate/TIBA

Ali, Amjad; Liu, Xiaoyu; Guo, Yintian; Akram, Muhammad; Wu, Haifeng; Liu, Wucan; Khan, Abid; Jiang, Baiyu; Fu, Zhisheng; Fan, Zhiqiang

doi:10.1016/j.jorganchem.2020.121366

Cited by 22 publications

(31 citation statements)

References 72 publications

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“…Similar phenomena have been found in the previous studies of our group on ethylene and propylene polymerizations with Mt-II/MMAO, where the [C * ]/[M] level was about 70% in the ethylene system and lower than 30% in propylene polymerization (see Table 5 ) [ 30 , 39 , 51 ] It has been explained that the active centers producing polypropylene should be loosely associated ion pairs but not contact ion pairs, since the high steric hindrance in active centers with contact ion pairs will prohibit coordination of the bulky propylene, but allow for ethylene coordination. Therefore, the lower [C*]/[M] level in propylene polymerization can be largely attributed to absence of contact ion pairs in its active center family.…”

Section: Resultssupporting

confidence: 89%

“…It is obvious that both Mt-I and Mt-II showed high activity in ethylene polymerization, with productivities between 3.17 × 10 6 g/mol Mt ·h to 5.06 × 10 6 g/mol Mt ·h. In our previous study on ethylene polymerization with Mt-II/MMAO and Mt-II/dMAO, productivities of 2.16 × 10 6 g/mol Mt ·h and 5.2 × 10 6 g/mol Mt ·h were observed, respectively [ 30 ]. The borate/alkylaluminum cocatalyst showed similar activity as that of aluminoxane-based cocatalyst.…”

Section: Resultsmentioning

confidence: 98%

“…The method of counting active center concentration by the quench-labeling method using TPCC as the quencher has been successfully applied in this study on ethylene and propylene polymerization with Mt-I/borate/TIBA and Mt-II/borate/TIBA. This method has been used in our previous systematical comparative studies on the kinetics of ethylene and propylene polymerizations with Mt-I and Mt-II using borate/alkylaluminum as the activator [ 30 ]; the same method has been used to study the effects of alkylaluminum cocatalyst on active fraction ([C*]/[Zr]). Detailed kinetics of zirconium catalyzed ethylene polymerization provides key information for understanding the mechanism of these important industrial processes.…”

Section: Resultsmentioning

confidence: 99%

“…The sulfur content of a blank polyethylene sample synthesized at the same conditions without the quenching step was found to be nearly 0, in contrast to the 5–25 ppm sulfur content of the quench-labeled samples. The relative error of the measurement was about 5% [ 26 , 30 ].…”

Section: Methodsmentioning

confidence: 99%

“…It is obvious that the kinetic studies based on direct counting of the [C*]/[Z] concentration in the polymer reaction system can permit the easier construction of a comprehensive mechanistic model. Many such studies have been reported based on different procedures of counting the active center concentration in homogenous metallocene catalyzed polymerization [ 26 , 27 , 28 , 29 , 30 ]. However, conflicting results of active centers values have been found in the literature while dealing with the same type of metallocene catalyzed polymerization, maybe because of different sensitivity levels of the methods that have been used [ 26 , 31 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

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Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure

et al. 2021

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The kinetics of ethylene and propylene polymerization catalyzed by homogeneous metallocene were investigated using 2-thiophenecarbonyl chloride followed by quenched-flow methods. The studied metallocene catalysts are: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I), rac-Et(Ind)2ZrCl2 (Mt-II) activated with ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II), and were co-catalyzed with different molar ratios of alkylaluminum such as triethylaluminium (TEA) and triisobutylaluminium (TIBA). The change in molecular weight, molecular weight distribution, microstructure and thermal properties of the synthesized polymer are discussed in detail. Interestingly, both Mt-I and Mt-II showed high activity in polyethylene with productivities between 3.17 × 106 g/molMt·h to 5.06 × 106 g/molMt·h, activities were very close to each other with 100% TIBA, but Mt-II/borate-II became more active when TEA was more than 50% in cocatalyst. Similarly, Polypropylene showed the highest activity of 11.07 106 g /molMt·h with Mt-I/Borate-I/TIBA. The effects of alkylaluminum on PE molecular weight were much more complicated; MWD curve changed from mono-modal in Mt-I/borate-I/TIBA to bimodal type when TIBA was replaced by different amounts of TEA. In PE, the active center fractions [C*]/[Zr] of Mt-I/borate were higher than that of Mt-II/borate and average chain propagation rate constant (kp) value slightly decreased with the increase of TEA/TIBA ratio, but the Mt-II/borate systems showed higher kp 1007 kp (L/mol·s). In PP, the Mt-I/borate presented much higher [C*]/[Zr] and kp value than the Mt-II. This work also extend to investigate the mechanistic features of zirconocenes catalyzed olefin polymerizations that addressed the largely unknown issues in zirconocenes in the distribution of the catalyst, between species involved in polymer chain growth and dormant state. In both metallocene systems, chain transfer with alkylaluminum is the dominant way of chain termination. To understand the mechanism of cocatalyst effects on PE Mw and (MWD), the unsaturated chain ends formed via β-H transfer have been investigated by 1H NMR analysis.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure

et al. 2021

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Improvement of catalytic activity for α‐diimine nickel complex with active sites stabilized by bulky boron counterions at elevated temperature

Wang

Feng

Guo

et al. 2022

Applied Organom Chemis

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Three α‐diimine Ni (II) catalysts (Cat.1, Cat.2 and Cat.3) were synthesized and investigated for ethylene polymerization using alkyl aluminum and organoboron compounds as binary cocatalyst. The effects of different alkyl aluminum and boron complexes on ethylene polymerization catalyzed by Cat.1, Cat.2, and Cat.3 were studied. The sodium tetrakis[3,5‐bis (trifluoromethyl)phenyl]borate (NaBArF) was found to have best promotion for the catalytic activity of Cat.1, compared to negative effect of dimethylanilinium tetrakis (pentafluorophenyl)borate (TTB) and trityl tetrakis (pentafluorophenyl)borate (AB). All the three catalysts showed higher catalytic activity when NaBArF was introduced into the catalytic system, especially for Cat.3 (increased by 41.3% at 70°C). There was still minor increase of the catalytic activity for Cat.2 which have much better thermostability than Cat.3. The charging sequence of NaBArF and the [B]/[Ni] ratio have significant effects on the catalytic activity. The better catalytic performance of Cat.1/AlEt2Cl/NaBArF could be explained by its ability to raise the number of active centers. Namely, the molar percentage of active centers of Cat.1/AlEt2Cl/NaBArF was still above 30%, which was 1.7 times that of Cat.1/AlEt2Cl even if polymerization ran up to 30 min based on 2‐thiophenecarbonyl chloride (TPCC) quench‐labeling method. Lower [Al]/[Ni] ratio but more active centers and longer active centers lifetime of this binary cocatalyst is promising for improving the activity of ethylene polymerization industrially at elevated temperature.

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Activation of Substituted Metallocene Catalysts Using Methylaluminoxane

Collins

Linnolahti

2022

ChemCatChem

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Activation of the metallocene complexes (n-C 4 H 9 -(η 5 -C 5 H 4 )) 2 ZrCl 2 (BuCp 2 ZrCl 2 ) and rac-1,2-ethylenebis(1-η 5 -C 9 H 6 )ZrCl 2 (EBIZrCl 2 ) using methylaluminoxane (MAO) was investigated by electrospray ionization mass spectrometry (ESI-MS). Formation of dinuclear complexes at low Al : Zr ratios, which is accompanied by catalyst deactivation, occurs in the former case. In contrast, this behavior was not observed at similar Al : Zr ratios in the case of the EBIZrCl 2 complex. Both active [BuCp 2 ZrMe 2 AlMe 2 ][MAO(Me)] 3 and deactivated [(BuCp 2 Zr) 2 (μ-CH 2 )μ-Cl][MAO(Me)] 9 complexes were detected in leaching experiments using a SiO 2 -MAO-supported BuCp 2 ZrCl 2 catalyst and excess MAO. DFT studies of the structure and UV-Vis spectra calculated for the dinuclear cations 9 detected by ESI-MS suggest that these species may account for long-wavelength absorption seen in experimental spectra of complexes like BuCp 2 ZrCl 2 upon activation with MAO.

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Kinetics and mechanism of ethylene and propylene polymerizations catalyzed with ansa-zirconocene activated by borate/TIBA

Cited by 22 publications

References 72 publications

Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure

Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure

Improvement of catalytic activity for α‐diimine nickel complex with active sites stabilized by bulky boron counterions at elevated temperature

Activation of Substituted Metallocene Catalysts Using Methylaluminoxane

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