Condensed-Mode Cooling for Ethylene Polymerization: The Influence of Inert Condensing Agent on the Polymerization Rate

• Published in: Macromolecular chemistry and physics 2014-05, Vol.215 (9), p.873-878
• Main Authors: Namkajorn, Montree, Alizadeh, Arash, Somsook, Ekasith, McKenna, Timothy F. L.
• Format: Article
• Language: English
• Subjects: Addition polymerization; Applied sciences; Chemical Sciences; Condensing; Diffusivity; Ethylene; ethylene polymerization; Exact sciences and technology; Fluidized bed reactors; Inert; inert condensing agents; Organic polymers; Partial pressure; Physicochemistry of polymers; polymer morphology; Polymerization; Polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Solubility; sorption; supported catalysts; Surface chemistry
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/macp.201300757

Inert condensing agents (ICAs) are used principally to cool down gas‐phase fluidized bed reactors used to polymerize ethylene over supported catalysts. While these ICAs are chemically inert, it appears that they might nevertheless increase the polymerization rate. n‐Hexane is used as an ICA, and an enhancement in the instantaneous rate of ethylene polymerization in the gas phase is observed. This is attributed to a rise in the local ethylene concentration in the amorphous polymer phase surrounding the active sites, due to increases in both the solubility and diffusivity of ethylene in the amorphous polymer. In addition, the polymer particles have a smoother surface with less formation of fiber‐like substructures as the n‐hexane concentration increases. The promotion of the local ethylene concentration in amorphous polymer phase surrounding active sites, due to increase in both the solubility and diffusivity of the ethylene in the polymer, results in the enhancement of the instantaneous rate of ethylene poly­merization in the presence of n‐hexane. In addition, as the partial pressure of n‐hexane increases, the particles have a much smoother surface with a regular morphology.