Search results for "Polymerization of ethylene"
showing 3 items of 13 documents
Organometallic VCl4-based catalyst supported on MgCl2(THF)2 for ethylene polymerization
1997
A Ziegler-Natta catalyst was obtained by milling VCl4 with the magnesium support in the from of the MgCl2(THF)2 complex, followed by activation with an organoaluminum compound. This catalyst was employed in low-pressure polymerization of ethylene. The system was found to offer a very high activity and to polymerize ethylene at a rate of a few hundred kg PE/(g Vh) with the resulting molecular weight of the product very high. The kinetic investgation of the polymerization process revealed over 80 % of the transition metal atoms to be involved in the forming catalytic active sites, undergoing virtually no deactivation over the period of time studied.
Weryfikacja kinetycznego modelu polimeryzacji etylenu wobec metaloorganicznych katalizatorów wanadowych na nośniku magnezowym
1998
The kinetic studies are reviewed on low-pressure polymerization of ethylene over two types of organovanadium catalysts, viz., MgCl 2(THF) 2/VCl 4/Et 2AlCl and MgCl 2(THF) 2VOCl 3Et 2AlCl, each deposited on a magnesium carrier. The polymerization rate was found to be directly related to the catalyst and monomer concentrations (Figs. 2 and 3), unless when the access of the monomer to the reactive V-C bond is restricted by diffusion. Polymer chain termination step was found to result from the reaction of the transfer onto the monomer and to be associated with the regeneration of the active site on which a new macromolecule can be formed. A kinetic model was developed for the ethylene polymeriz…
Synthesis of oxide-supported vanadium catalysts and their activity in ethylene polymerization
1999
The activity of oxide-supported vanadium-based catalyst systems (VOCl 3/Et 2AlCl) in low-pressure ethylene polymerization and the properties of the resulting polyethylenes were studied in relation to the type and mode of modification of the oxide support. Alumina, silica and an un"conventional silica-type material prepared by the sol-gel process were used as supports. Results are compared with those obtained earlier with a catalyst supported on MgCl 2(THF) 2. Of the oxides studied, the silica-type sol-gel material dehydrated and subsequently modified with Et 2AlCl proved to be the best carrier for a vanadium catalyst. The polyethylene prepared by using this catalyst support was found to exh…