Plausible guard effect on the active sites of heterogeneous Ziegler–Natta catalyst by coordinating monomers and growing polymer chains in the initial stage of propene polymerization

2004 ◽  
Vol 53 (6) ◽  
pp. 723-727 ◽  
Author(s):  
Namiko Murayama ◽  
Boping Liu ◽  
Hisayuki Nakatani ◽  
Minoru Terano
Keyword(s):  
Active Sites ◽  
Polymer Chains ◽  
Initial Stage ◽  
Propene Polymerization ◽  
Natta Catalyst ◽  
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 Isolated Ti(III) Species on the Surface of a Pre-active Ziegler Natta Catalyst

2020 ◽  
Vol 51 (11) ◽  
pp. 1515-1528
Author(s):  
Leonora Podvorica ◽  
Enrico Salvadori ◽  
Fabrizio Piemontesi ◽  
Gianni Vitale ◽  
Giampiero Morini ◽  
...  
Keyword(s):  
Active Sites ◽  
Binary Systems ◽  
Active Species ◽  
Lewis Bases ◽  
Quadrupole Interactions ◽  
Nuclear Quadrupole Interactions ◽  
Natta Catalyst ◽  
Pulse Epr ◽  
Nuclear Quadrupole ◽  
Ziegler Natta Catalyst

AbstractThe nature of Ti(III) species, introduced in working models of industrial Ziegler Natta catalyst precursors, consisting of MgCl2/TiCl4 binary systems, eventually containing different Lewis basis, are studied by a combination of X- and Q-band CW and pulse EPR spectroscopy. In Ziegler Natta catalysts, Ti(III) play the double role of active catalytic species and unconventional spin probes. On the binary system, two dominant Ti(III) species, characterized by distinctively different EPR spectra, are observed. 35,37Cl Q-Band HYSCORE spectra allow estimating the hyperfine and nuclear quadrupole interactions of directly coordinated Cl, characterized by a hyperfine dipolar contribution of the order of 5 MHz and nuclear quadrupole interactions of the order of e2qQ/h = 9 MHz. Interestingly, the two dominant EPR active species are selectively suppressed by the presence of different Lewis bases, indicating the possibility to address the long standing issue of the influence of Lewis bases in driving specific morphological configurations and influencing the catalytic properties of Ti(III) active sites.

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