FTIR INVESTIGATION OF ETHYLENE COORDINATION AND POLYMERIZATION ON REDUCED CR/SIO2 CATALYST

FTIR spectroscopy was applied to study the initial steps of ethylene polymerization on reduced chromia-silica (0.5 wt% Cr/SiO2). To decrease the speed of the reaction small doses of gas were introduced to the catalyst in each run and C2D4 was used to confirm band assignments. At the initial steps of the reaction only ethylene molecules coordinated to probably Cr(A)2+ cations were observed. The concentration of such complexes was estimated to be about 50% of the total amount of Cr atoms in the sample. The FTIR spectrum of the polymer formed at the initial doses of C2H4 (when [C2H4] almost-equal-to [Cr]) was found to be slightly different from that formed after excess ethylene was introduced onto the catalyst ([C2H4] > [Cr]).