Search results for "Ziegler–Natta catalysts"
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Ziegler–Natta catalysts based on vanadium halides: a DFT study
2003
Abstract Ziegler–Natta ethylene insertion into the carbon–metal bond for a number of fragments containing vanadium on different oxidation states as well as the halogen ligands has been studied by means of DFT. It is shown that the complexation and insertion energies are strongly influenced by the charge on the transition metal atom and, to some extent, by the electronegativity of the halogen atom. Complexation energy varies in the range −129 to −159 kJ/mol for charged species and −64 to −77 kJ/mol for neutral ones. Insertion energy follows a similar pattern and ranges from −28 to −62 and −82 to −100 kJ/mol, respectively. The calculated values are compared with the experimental results and d…
Microstructure of ethylene-1-hexene and ethylene-1-octene copolymers obtained over Ziegler–Natta catalysts supported on MgCl 2 (THF) 2
2001
Abstract The ethylene copolymerizations with 1-hexene or 1-octene in the presence of hydrogen using three catalysts, MgCl 2 (THF) 2 /VOCl 3 /Et 2 AlCl, MgCl 2 (THF) 2 /VCl 4 /Et 2 AlCl, MgCl 2 (THF) 2 /TiCl 4 /Et 2 AlCl, were investigated. It was found that the addition of hydrogen into the copolymerization feed reduces the molecular weight of the copolymers produced and decreases the activity of all the studied catalysts. The microstructure of the copolymers obtained was determined on the basis of 13 C NMR investigations and the reactivity ratios of the comonomers were calculated. The lack of tendency of the olefin comonomers to the creation of the polymer block was confirmed. It was found…