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Type: Artigo de periódico
Title: Gas-phase polymerization of ethylene using supported metallocene catalysts: Study of polymerization conditions
Author: Tannous, K
Soares, JBP
Abstract: The influence of polymerization conditions on the gas-phase polymerization of ethylene with a supported metallocene catalyst (Cp2ZrCl2/SiO2) was investigated. The experiments were carried out in a 1.0-L semi-batch autoclave reactor and in a 0.6-L glass reactor, at pressures up to 100 psi and temperatures up to 57degreesC. Anchor and helicoidal agitators were used. Trimethylaluminium (TMA) and methylaluminoxane (MAO) were used as cocatalysts. Hydrogen was used as the chain-transfer agent. The polymer products were characterized by gel permeation chromatography (GPC) and scanning electron microscopy (SEM). Effects of pre-contact time of the catalyst and cocatalyst, catalyst injection configuration, agitator design, hydrogen volume, polymerization temperature and pressure were studied. The heterogeneity of polymer particles inside different zones of the reactor was also verified. The results indicated that several of these factors were crucial to obtain well-controlled gas-phase polymerization. SEM analyses showed that irregular growth of polymer within the shells often formed polymer particles of irregular shape. Flory's distribution was used to describe the polymerization mechanism for each site type. Interactions between catalyst sites and support surface are considered to broaden these distributions. Several Flory's distributions (4 to 7 different site types) were required to describe the broad and sometimes multimodal molecular weight distributions. Mass and heat transfer resistances may also be important in further broadening these distributions.
Subject: gas-phase polymerization
metallocene catalysts
molecular weight distribution
scanning electronic microscopy
Country: Alemanha
Editor: Wiley-v C H Verlag Gmbh
Citation: Macromolecular Chemistry And Physics. Wiley-v C H Verlag Gmbh, v. 203, n. 13, n. 1895, n. 1905, 2002.
Rights: fechado
Identifier DOI: 10.1002/1521-3935(200209)203:13<1895
Date Issue: 2002
Appears in Collections:Unicamp - Artigos e Outros Documentos

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