Abstract
The catalysts prepared from the trivalent and divalent chromium compounds under conditions that prevented their oxidation were investigated in the reaction of ethylene polymerization. Also the reduced chromia catalyst prepared by standard method from sexivalent chromium compound was investigated. The valence and coordinate states of chromium ions in the catalysts were determined by EPR and reflectance optical spectroscopy. In all cases, the catalysts prepared from trivalent chromium ions had a large activity; whereas the catalysts from divalent chromium had no activity. The reduction of the trivalent chromium ions into divalent state sharply decreased the activity. The activity of the catalysts prepared by the standard method was also decreased under reduction. It is concluded that the exposed Cr 3+ ions in low coordination state are responsible for the catalytic activity of the catalysts.
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