Ferrous rather than ferric species are the active sites in bis(imino)pyridine iron ethylene polymerization catalysts

2004 ◽  
Vol 5 (1) ◽  
pp. 45-48 ◽  
Author(s):  
Konstantin P. Bryliakov ◽  
Nina V. Semikolenova ◽  
Vladimir N. Zudin ◽  
Vladimir A. Zakharov ◽  
Evgenii P. Talsi
Keyword(s):  
Ethylene Polymerization ◽  
Active Sites ◽  
Polymerization Catalysts

scholarly journals Spectroscopic Signature and Structure of Active Sites in Ziegler-Natta Polymerization Catalysts revealed by Electron Paramagnetic Resonance

2021 ◽  
Author(s):  
Anton Ashuiev ◽  
Matthieu Humbert ◽  
David Gajan ◽  
Sebastien Norsic ◽  
Jan Blahut ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Ethylene Polymerization ◽  
Active Sites ◽  
Active Species ◽  
Atomic Scale ◽  
Polymerization Catalysts ◽  
Paramagnetic Resonance ◽  
Spectroscopic Signatures ◽  
Electron Paramagnetic ◽  
Ziegler Natta Catalysts

Despite decades of extensive studies, the atomic-scale structure of the active sites in heterogeneous Ziegler-Natta (ZN) catalysts, one of the most important processes of the chemical industry, remains elusive and a matter of debate. In the present work, the structure of “active sites” of ZN catalysts in the absence of ethylene, referred to as “dormant active sites”, is elucidated from magnetic resonance experiments, carried out on samples reacted with increasing amounts of BCl<sub>3</sub> so as to enhance the concentration of active sites and observe clear spectroscopic signatures. Using EPR and NMR spectroscopies, in particular 2D HYSCORE experiments complemented by DFT calculations, we show that the activated ZN catalysts contain bimetallic alkyl-Ti(III),Al species whose amount is directly linked to the polymerization activity of MgCl<sub>2</sub>-supported Ziegler-Natta catalysts. This connects those spectroscopic signatures to the active species formed in the presence of ethylene, and enables us propose an ethylene polymerization mechanism on the observed bimetallic alkyl-Ti(III),Al species based on DFT computations<br>

Doubly fused N,N,N-Iron Ethylene Polymerization Catalysts appended with Fluoride Substituents; probing catalytic performance via a combined experimental and MLR study

2021 ◽  
Author(s):  
Qiuyue Zhang ◽  
Wenhong Yang ◽  
Zheng Wang ◽  
Gregory A. Solan ◽  
Tongling Liang ◽  
...  
Keyword(s):  
Ethylene Polymerization ◽  
Catalytic Performance ◽  
Chloride Complex ◽  
Polymerization Catalysts

Access to six examples of α,α’-bis(imino)-2,3:5,6-bis(pentamethylene)pyridine-iron(II) chloride complex, [2,3:5,6-{C4H8C(N(2-R1-4-R3-6-R2C6H2)}2C5HN] (R1 = Me, R2 = R3 = CH(p-FPh)2 Fe1; R1 = Et, R2 = R3 = CH(p-FPh)2 Fe2; R1 = iPr,...

scholarly journals Chromium ethylene polymerization catalysts bearing sterically enhanced α,α′-bis(imino)-2,3:5,6-bis(pentamethylene)pyridines: Tuning activity and molecular weight

Polymer ◽  
2019 ◽  
Vol 171 ◽  
pp. 87-95 ◽  
Author(s):  
Chantsalnyam Bariashir ◽  
Zheng Wang ◽  
Gregory A. Solan ◽  
Chuanbing Huang ◽  
Xiang Hao ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ethylene Polymerization ◽  
Polymerization Catalysts
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