a fi zr-based catalyst of bis[n-(3,5-dicumylsalicylidene)-2′,6′­diisopropylanilinato]zirconium(iv) dichloride was prepared and used for polymerization of ethylene. the effects of reaction conditions on the polymerization were examined in detail. the increase in ethylene pressure and rise in polymerization temperature up to 35 oc were favorable for catalyst/mao to raise the catalytic activity as...

The copolymerizations of a gaseous monomer (ethylene) and a liquid monomer (vinyl acetate) via emulsion and miniemulsion polymerizations are reported. Reactions in which the vinyl acetate was introduced in both batch and semibatch modes are carried out. (Ethylene introduction is always in a semibatch model since the polymerization is carried out under a constant pressure of ethylene in the reac...

heterogeneous ziegler-natta and homogeneous metallocene catalysts exhibit greatly different active sitenature in olefin polymerization. in our previous study, it was reported that mgcl2-supported titanocenecatalysts can generate both ziegler-natta-type and metallocene-type active sites according to the type of activators.the dual active site nature of the supported titanocene catalysts was furt...

The elementary processes involved in the polymerization of ethylene by soluble Ziegler catalysts of the type Cp2TiMeCl/AlMeCl2 have been studied by C N M R spectroscopy. Using Cenriched ethylene, detailed information was obtained directly on the system in the course of the polymerization. No spectroscopic evidence was found for precoordination of the monomer. The development of the oligomer dis...

Free radical polymerization of ethylene in an intermediate pressure and temperature range (P(ethylene) < 250 bar and 50 °C < T < 90 °C) in the presence of an organic solvent has been studied. Under selected conditions (P, T) and according to the amount of organic solvent added, either a supercritical monophasic or a biphasic medium is obtained. In the case of a biphasic medium, polymerization o...

Ethylene polymerization was carried out using Phillips chromium catalyst based on silica supports such as silica aerogel, SiO2 (Grace 643), and titanium modified SiO2 (G 643), and the results were compared with other catalysts based on SiO2 (Aldrich), SBA-15(Hex), SBA-15(Sp) and MCM-41. A combination of TGA, DSC, XRD, nitrogen adsorption, SEM, ICP, FTIR and other analyses were used to character...

Catalytic polymerization of ethylene in aqueous emulsion by in situ catalysts based entirely on compounds commercially available from standard chemicals suppliers, namely a chlorinated derivative of 1,4-benzoquinone, triphenylphosphine, and bis(1,5-cyclooctadiene)nickel, is reported. Using miniemulsions of catalyst solutions in a small amount of hydrocarbon solvent for polymerization, stable di...

A series of binuclear nickel/palladium catalysts C4-C7 with conjugated α-diimine ligands were designed, prepared and fully characterized. The binuclear nickel complexes C6 and C7 were activated by modified methylalumoxanes (MMAO) to generate highly active ethylene polymerization catalysts with activities up to 1050 kg [mol (Ni) h](-1). The activity of C7 is twice that of the mononuclear analogu...

Ring-opening polymerization (ROP) of ethylene carbonate (EC) is associated with the emission of carbon dioxide during polymerization, which results in polymer chains containing ether linkages besides targeted carbonate linkages. In this study, ethylene carbonate is polymerized by ring-opening polymerization in the presence of sodium stannate trihydrate as a heterogeneous transesterification cat...

Cyclopentadienyl-titanium complexes containing –OC6H4X ligands (X = Cl, CH3) activated with methylaluminoxane (MAO) were used in the homo-polymerization of ethylene, propylene, 1-butene, 1-pentene, 1-butene, and 1-hexene, and also in copolymerization of ethylene with the α-olefins mentioned. The -X substituents exhibit different electron donor-acceptor properties, which is described by Hammett’...