title: Real-time Analysis of a Working Triethylaluminium-Modified Cr/Ti/SiO2Ethylene Polymerization Catalyst with In Situ Infrared Spectroscopy.
abstract: A diffuse reflectance infrared Fourier-transform (DRIFT) study has been conducted at 373 K and 1 bar on an industrial Cr/Ti/SiO2Phillips-type catalyst modified with, and without, triethylaluminium (TEAl) as co-catalyst. The reaction rate of the polymerization of ethylene, as monitored by the increase in the methylene stretching band of the growing polyethylene (PE), has been investigated as a function of the titanium content. After an initial period of mixed kinetics, with the reaction rate significantly higher for the TEAl-modified catalysts compared with the non-modified catalysts, the polymerization proceeded as a pseudo-zero-order reaction with a reaction rate that increased as a function of titanium loading. Furthermore, it was found that the higher Ti loading caused the appearance of more acidic hydroxyl groups and modified the Cr sites by making them more Lewis acidic, ultimately shortening the induction time and increasing the initial polymerization rate.
authors.affiliation: Inorganic Chemistry and Catalysis Debye Institute for Nanomaterials Science Utrecht University Universiteitsweg 99 3584 CG Utrecht The Netherlands.
authors.forename: Dimitrije
authors.initials: D
authors.lastname: Cicmil
authors.affiliation: Refining & Chemicals Total Research and Technology Feluy Zone Industrielle C B-7181 Seneffe Belgium.
authors.forename: Jurjen
authors.initials: J
authors.lastname: Meeuwissen
authors.affiliation: Refining & Chemicals Total Research and Technology Feluy Zone Industrielle C B-7181 Seneffe Belgium.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Vantomme
authors.affiliation: Inorganic Chemistry and Catalysis Debye Institute for Nanomaterials Science Utrecht University Universiteitsweg 99 3584 CG Utrecht The Netherlands.
authors.forename: Bert M
authors.initials: BM
authors.lastname: Weckhuysen
keywords: Phillips catalyst; diffuse reflectance Fourier-transform infrared spectroscopy; heterogeneous catalysis; polyethylene; triethylaluminium