Stereospecific Nature of Active Sites on TiCl4/MgCl2 Ziegler–Natta Catalyst in the Presence of an Internal Electron Donor

2003 ◽  
Vol 204 (3) ◽  
pp. 395-402 ◽  
Author(s):  
Boping Liu ◽  
Takashi Nitta ◽  
Hisayuki Nakatani ◽  
Minoru Terano
Keyword(s):  
Electron Donor ◽  
Active Sites ◽  
Natta Catalyst ◽  
Internal Electron ◽  
Ziegler Natta Catalyst

Toward an Understanding of the Molecular Level Properties of Ziegler−Natta Catalyst Support with and without the Internal Electron Donor

2010 ◽  
Vol 115 (5) ◽  
pp. 1952-1960 ◽  
Author(s):  
K. S. Thushara ◽  
Edwin S. Gnanakumar ◽  
Renny Mathew ◽  
Ratnesh K. Jha ◽  
T. G. Ajithkumar ◽  
...  
Keyword(s):  
Electron Donor ◽  
Molecular Level ◽  
Catalyst Support ◽  
Natta Catalyst ◽  
Internal Electron ◽  
Ziegler Natta Catalyst

scholarly journals Multiplicity of Active-Site in Heterogeneous Ziegler-Natta Catalyst and Its Correlation with Polymer Microstructure

1970 ◽  
Vol 46 (4) ◽  
pp. 487-494
Author(s):  
ATM Kamrul Hasan
Keyword(s):  
Molecular Weight ◽  
Computer Simulation ◽  
Active Site ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Chain Structure ◽  
Surface Complexes ◽  
Polymer Microstructure ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

Multiplicity of active-site in heterogeneous Ziegler-Natta catalysts and its correlation with polymer microstructure was studied through the surface structure analysis of catalyst by computer simulation of X-ray Photoelectron Spectroscopy (XPS) data and microstructure investigation of polypropylene chains based on the deconvolution of the molecular weight distribution curves by multiple Flory most probable distributions using Gel Permeation Chromatography (GPC) method. The number and relative intensities of these peaks were found correlated to the distribution of multiple active sites. In this investigation, four individual categories of active sites were identified, each of which yields polypropylene with unique properties of molecular weight and chain structure different from other active sites. The reason of the multiplicity of active sites was determined by the presence of different locations of surface titanium species coordinated with other surface atoms or molecules. These different surface complexes of active species determine the multiple active site nature of catalyst which replicates the microtacticity, molecular weight and chain microstructure distribution of polymer. Keywords: Ziegler-Natta catalyst; Multiple active sites; Flory components; Computer simulation; Deconvolution; MWD. DOI: http://dx.doi.org/10.3329/bjsir.v46i4.9596 BJSIR 2011; 46(4): 487-494

POISONING OF ACTIVE SITES ON ZIEGLER-NATTA CATALYST FOR PROPYLENE POLYMERIZATION

2008 ◽  
Vol 26 (05) ◽  
pp. 547 ◽  
Author(s):  
Kitti Tangjituabun ◽  
Sang Yull Kim ◽  
Yuichi Hiraoka ◽  
Toshiaki Taniike ◽  
Minoru Terano ◽  
...  
Keyword(s):  
Active Sites ◽  
Propylene Polymerization ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

scholarly journals Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 358 ◽  
Author(s):  
Zhen Zhang ◽  
Baiyu Jiang ◽  
Feng He ◽  
Zhisheng Fu ◽  
Junting Xu ◽  
...  
Keyword(s):  
Propylene Polymerization ◽  
Lamellar Thickness ◽  
Efficient Catalyst ◽  
Two Systems ◽  
Key Factor ◽  
Natta Catalyst ◽  
Internal Electron ◽  
20 Nm ◽  
Kinetics Of ◽  
Ziegler Natta Catalyst

The kinetic behaviors of ethylene and propylene polymerizations with the same MgCl2-supported Ziegler–Natta (Z–N) catalyst containing an internal electron donor were compared. Changes of polymerization activity and active center concentration ([C*]) with time in the first 10 min were determined. Activity of ethylene polymerization was only 25% of that of propylene, and the polymerization rate (Rp) quickly decayed with time (tp) in the former system, in contrast to stable Rp in the latter. The ethylene system showed a very low [C*]/[Ti] ratio (<0.6%), in contrast to a much higher [C*]/[Ti] ratio (1.5%–4.9%) in propylene polymerization. The two systems showed noticeably different morphologies of the nascent polymer/catalyst particles, with the PP/catalyst particles being more compact and homogeneous than the PE/catalyst particles. The different kinetic behaviors of the two systems were explained by faster and more sufficient catalyst fragmentation in propylene polymerization than the ethylene system. The smaller lamellar thickness (<20 nm) in nascent polypropylene compared with the size of nanopores (15–25 nm) in the catalyst was considered the key factor for efficient catalyst fragmentation in propylene polymerization, as the PP lamellae may grow inside the nanopores and break up the catalyst particles.

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