INFRARED SPECTRAL CHARACTERIZATION OF SUPPORTED PROPENE POLYMERIZATION CATALYSTS - A LINK TO CATALYST PERFORMANCE

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 nu-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 nu-C = O band ideally present). Catalysts prepared from water- and OH-contaminated starting materials are characterized by the presence of nu-OH bands, whose increasing relative intensity indicates progressive deterioration in catalyst performance.