Special features of the bulk polymerization of propylene on a titanium-magnesium catalyst in the presence of hydrogen

Aladyshev, A. M.; Isichenko, O.P.; Недорезова, П. М.; Tsvetkova, B.I.; Gavrilov, Yu. A.; D'yachkovskii, F.S.

doi:10.1016/0032-3950(91)90045-r

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…Figure 3 illustrates the reaction kinetics in runs 1P and 3P. As expected,16, 17, 19–23 the polymerization rate in the presence of hydrogen is significantly higher. A mechanistic explanation of this effect23 is discussed subsequently.…”

Section: Resultssupporting

confidence: 63%

Multicenter nature of titanium‐based Ziegler–Natta catalysts: Comparison of ethylene and propylene polymerization reactions

Kissin

2003

J. Polym. Sci. A Polym. Chem.

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This article discusses the similarities and differences between active centers in propylene and ethylene polymerization reactions over the same Ti-based catalysts. These correlations were examined by comparing the polymerization kinetics of both monomers over two different Ti-based catalyst systems, ␦-TiCl 3 -AlEt 3 and TiCl 4 / DBP/MgCl 2 -AlEt 3 /PhSi(OEt) 3 , by comparing the molecular weight distributions of respective polymers, in consecutive ethylene/propylene and propylene/ethylene homopolymerization reactions, and by examining the IR spectra of "impact-resistant" polypropylene (a mixture of isotactic polypropylene and an ethylene/propylene copolymer). The results of these experiments indicated that Ti-based catalysts contain two families of active centers. The centers of the first family, which are relatively unstable kinetically, are capable of polymerizing and copolymerizing all olefins. This family includes from four to six populations of centers that differ in their stereospecificity, average molecular weights of polymer molecules they produce, and in the values of reactivity ratios in olefin copolymerization reactions. The centers of the second family (two populations of centers) efficiently polymerize only ethylene. They do not homopolymerize ␣-olefins and, if used in ethylene/␣-olefin copolymerization reactions, incorporate ␣-olefin molecules very poorly.

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Section: Resultssupporting

confidence: 63%

Multicenter nature of titanium‐based Ziegler–Natta catalysts: Comparison of ethylene and propylene polymerization reactions

Kissin

2003

J. Polym. Sci. A Polym. Chem.

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“…First, hydrogen significantly activates MgCl 2 ‐supported Ziegler–Natta catalysts in propylene polymerization reactions, in terms of both the overall polymer yields and the initial reaction rates 1–8. The effect is reversible; removal of hydrogen brings the polymerization rate down, and reinstitution of hydrogen results in reactivation of the catalysts 2, 5, 9. A previous article10 describes a chemical mechanism that we have proposed to explain this effect.…”

Section: Introductionmentioning

confidence: 95%

Hydrogen effects in propylene polymerization reactions with titanium‐based Ziegler–Natta catalysts. II. Mechanism of the chain‐transfer reaction

Kissin

Rishina

Vizen

2002

J. Polym. Sci. A Polym. Chem.

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Hydrogen is a very effective chain-transfer agent in propylene polymerization reactions with Ti-based Ziegler-Natta catalysts. However, measurements of the hydrogen concentration effect on the molecular weight of polypropylene prepared with a supported TiCl 4 /dibutyl phthalate/MgCl 2 catalyst show a peculiar effect: hydrogen efficiency in the chain transfer significantly decreases with concentration, and at very high concentrations, hydrogen no longer affects the molecular weight of polypropylene. A detailed analysis of kinetic features of chain-transfer reactions for different types of active centers in the catalyst suggests that chain transfer with hydrogen is not merely the hydrogenolysis reaction of the TiOC bond in an active center but proceeds with the participation of a coordinated propylene molecule.

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“…The reaction rate is calculated from the amount of monomer fed to the reactor. Alladyshev et al [23] studied liquid propylene polymerization in fully-filled reactors. These authors determined the polymerization rate using the amount of propylene charged into the reactor in order to keep reactor pressure constant.…”

Section: Compensation Dilatometrymentioning

confidence: 99%

Estimation of the Polymerization Rate of Liquid Propylene Using Adiabatic Reaction Calorimetry and Reaction Dilatometry

Ali

Betlem

Roffel

et al. 2007

Macro Reaction Engineering

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The use of pressure‐drop and constant‐pressure dilatometry for obtaining rate data for liquid propylene polymerization in filled batch reactors was examined. The first method uses reaction temperature and pressure as well as the compressibility of the reactor contents to calculate the polymerization rate; in the second, the polymerization rate is calculated from the monomer feed rate to the reactor. Estimated polymerization rates compare well to those obtained using the well‐developed isoperibolic calorimetry technique, besides pressure‐drop dilatometry provides more kinetic information during the initial stages of the polymerization than the other methods.magnified image

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Special features of the bulk polymerization of propylene on a titanium-magnesium catalyst in the presence of hydrogen

Cited by 5 publications

References 7 publications

Multicenter nature of titanium‐based Ziegler–Natta catalysts: Comparison of ethylene and propylene polymerization reactions

Multicenter nature of titanium‐based Ziegler–Natta catalysts: Comparison of ethylene and propylene polymerization reactions

Hydrogen effects in propylene polymerization reactions with titanium‐based Ziegler–Natta catalysts. II. Mechanism of the chain‐transfer reaction

Estimation of the Polymerization Rate of Liquid Propylene Using Adiabatic Reaction Calorimetry and Reaction Dilatometry

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