Search results for "Natta"

Two-step polymerization of propylene over MgCl2-supported titanium catalyst

1998

The prepolymerization effect on propylene polymerization in the presence of a MgCl 2 -supported titanium catalyst was studied. The catalyst was pre-activated by polymerizing a small amount of propylene in the presence of Et 3 Al and cyclohexylmethyldimethoxysilane under mild conditions, and then it was used in a second step of propylene polymerization. Comparative studies of the polymerization process involving the investigated catalyst and its unmodified counterpart showed the rate-enhancement effect of prepolymerization and the same molecular weights, MWD's and isotacticities of the polymers obtained. Concentrations of active sites and propagation rate as well as transfer rate constants w…

A New Supported Zirconocene Catalyst for Ethylene Polymerization

1999

Metallocene catalysts enable the structure of polymers to be tailored in a way which has not been reached before. However, they are more active than the conventional Ziegler — Natta catalysts only as homogeneous metalocene systems, a fact that has essentially restricted their use to industrial processes producing polymers in solution. Modern polymerization processes are solvent free slurry (with liquid monomer) or gas phase processes. To use metallocene catalysts in these modern processes, it is necessary to convert them to heterogeneous catalysts [1, 2]. However, problems have appeared chiefly concerning the activity of the supported catalysts, because heterogeneous metallocene catalysts a…

Olefin Polymerisation Catalysts

2002

Polyolefins, which are products of polymerisation of unsaturated hydrocarbons of the olefin series, have a molecular weight in the range from several thousands to several millions. Depending on the type of monomer and method and mechanism of polymerisation the resulting polyolefins may differ in their structure and molecular weight. They can be used in many applications, for example as constructional plastics and in packaging, fibres, rubbers, and also as additives to control the viscosity of motor oils(1). As regards their scale of production polyolefins occupy the top position among mass-produced polymers(2).

Synthesis, characterization and catalytic properties for olefin polymerization of two new dimeric zirconium(IV) complexes having diamine-bis(phenolat…

2015

Abstract Reaction of the zirconium tetrachloride with one equivalent of the sodium salt of the diamine bis (phenolate) ligand, L1H2 (Me2NCH2CH2N-(CH2-2-OH-3,5-tBu-C6H2)2) or L2H2 (Me2NCH2CH2N-(CH2-2-OH-3,5-tBu-C6H2)(CH2-2-OH-C6H4)) in the presence of air led to formation of [Lig1ZrCl]2(μ-O) and [Lig2ZrCl]2(μ-O), respectively. These novel oxo-bridged dinuclear zirconium complexes were characterized by elemental analysis, 1H NMR spectroscopy and by single-crystal X-ray diffraction. Their reactivities in polymerization of ethylene and 1-octene, upon activation with Al(iBu)3/Ph3CB(C6F5)4 and MAO, were examined. It was found that lack of t-Bu substituents on one phenolate ring cause a significan…

The Number of Active Sites for the Polymerization of Ethylene, Propylene and Butene-1 by Ziegler-Natta Catalyst

1975

Polymerization of ethylene and propylene with ziegler-natta catalysts

2007

Synthesis and characterization of ethylene-1-hexene copolymers prepared by using MgCl2(THF)2-supported Ziegler-Natta catalysts

2000

Ethylene was copolymerized with 1-hexene over vanadium (VOCl3 and VCl4) and titanium (TiCl4) catalysts supported on MgCl2(THF)2 and activated with Et2AlCl. So far these catalyst systems have not been known as initiators of ethylene-1-hexene copolymerization. The vanadium catalysts were more active than the titanium catalyst and, at identical comonomer concentrations in the feed, gave rise to a greater incorporation of 1-hexene into the copolymer. Even at relatively low fractions of 1-hexene, the MgCl2(THF)2-supported catalysts affected much the copolymer properties like density, melting point and crystallinity.

Rypsimetyyliesterin tuotantopotentiaali, energiataseet ja kannattavuuslaskelma maatilamittakaavaiselle valmistukselle

2007

Kompleksy metali przejściowych z zasadami Lewisa jako prekursory katalizatorów polimeryzacji olefin. Cz. I. Postęp w komputerowym modelowaniu procesu…

2001

A review with 35 references covering molecular modeling in coordination polymerization over homogeneous and heterogeneous Ziegler-Natta catalysts. The study includes supports, cocatalysts, Lewis bases and solvents. Recent progress in elucidating the mechanisrn of elementary polymerization steps is presented against the background of rapidly deveIoping computational methods and available computational power. Theoretical studies on polymerization mcchanisms and structure of active centers are described (egns. 1-4). Authors own calculations are used to compare [MtC14(THF)2] complex-based (Mt = Ti, Hf or Zr) heterogeneous catalysts. The geometrical characteristics of precursors is presented (Ta…

Vanadium-based Ziegler-Natta catalyst supported on MgCl2(THF)2 for ethylene polymerization

1996

A supported magnesium‐vanadium‐aluminium catalyst was prepared by depositing –with the use of a milling technique–VOCl3 on the MgCl2(THF)2 support and subsequent activation with diethylaluminium chloride. Catalytic activity of the obtained system for ethylene polymerization was evaluated as a function of Mg/V and Al/V ratios as well as catalyst ageing time and polymerization temperature. High concentrations of THF in the catalytic system and considerable excess of an organoaluminium co‐catalyst were found to have no deactivating action on vanadium active sites. The catalyst obtained is stable and its activity for ethylene polymerization is high. It yields polyethylene with higher molecular …