Nicholas M. Karayannis

Infrared spectral characterization of supported propene polymerization catalysts: A link to catalyst performance

Abstract Characterization of supported propene polymerization catalysts, consisting of titanium chloride on a magnesium-based support with dibutyl phthalate as internal modifier, by means of infrared spectroscopy, proved useful not only in detecting improper catalyst preparation or contamination, but also in fairly accurately predicting catalyst polymerization performance. Inferior catalysts, activated at temperatures beyond the limits of the relatively narrow optimum temperature window, show significant spectral differences in comparison with properly activated catalysts; i.e., new v C O bands appear, owing to partial conversion of the internal modifier to phthaloyl mono- and dichlorides or coprecipitation of a titanium tetrachloride complex with dibutyl phthalate for activations at higher or lower than optimum temperatures, respectively. The activities of these inferior catalysts decrease progressively with increasing intensities of these new C O stretching absorption bands relative to that of the C O stretching mode of dibutyl phthalate coordinated to magnesium (the only v C O band ideally present). Catalysts prepared from water- and OH-contaminated starting materials are characterized by the presence of v OH bands, whose increasing relative intensity indicates progressive deterioration in catalyst performance.

12. Infrared Characterization of Supported Propylene Polymerization Catalysts-A Link to Catalyst Performance

Publisher Summary Catalyst IR characterization is not only useful in detecting either employment of improper activation temperatures or use of contaminated starting materials in catalyst preparation, but also can provide fairly accurate predictions regarding catalyst performance in propylene polymerizations. Current IR studies are directed toward the identification of additional characteristic catalyst absorption bands, as well as characterization of intermediate products of catalyst preparation. The chapter describes the IR method of characterization of supported polypropylene catalysts and its usefulness in predicting catalyst performance in some detail. During research on supported propylene polymerization catalysts, various regions of the IR, spectrum, including the far-IR region has been used to determine the presence of undesirable contaminants in the final catalysts, arising from either use of insufficiently pure raw materials or temperature deviations during catalyst activation. The catalysts studied, consisting of a titanium chloride-active species on a magnesium-containing support, and including dibutyl phthalate (DBP) as internal modifier, were prepared by employing standard procedures. An illustrative example of the effects of proper activation versus over or under activation is provided in the chapter, which shows performance, IR, and analytical data for a series of catalysts produced by activating aliquots of the same support batch at various temperatures in the 115–135°C range.

Organotin(IV) oxides and sulfides as modifiers of propene polymerization catalysts

Studies of a number of organotin(IV) oxides and sulfides as modifiers of Ziegler-type propene polymerization catalysts are reported. The general trend observed is that organotin(IV) sulfides provide better catalyst activity-stereospecificity combinations than the corresponding oxides. Among the various modifiers studied, μ-thiobis[tri-butyltin(IV)] was found to exhibit the best overall modifying effect. Combination of an organotin(IV) sulfide with a second modifier of the aromatic amine, N-oxide, phosphite ester or cyclic ether type in a binary modifier package was shown to lead to catalyst systems with excellent stereospecificities and activities ranging from acceptable to outstanding. Possible interactions and reactions of the organotin modifiers with the components of the catalyst system are discussed.