Characterization of a metallocene/co-catalyst system supported on silica by Fourier-Transform Raman spectroscopy

2,2′-bis-(indene-2-yl)-biphenyl-Zirconium dichloride (biph[2-Ind]2ZrCl2) supported on silica and in the presence of methylaluminoxane (MAO) cocatalyst was studied by FT-Raman spectroscopy. Even though the transition metal was present at a concentration down to 0.12 wt.%, useful FT-Raman spectra were obtained. The aim of this work was to correlate spectral features to such typical catalyst properties like Al/Zr ratio and catalytic yield (CY). The Raman spectra contain signals due to the co-catalyst and the catalyst. Catalyst signals due to ZrCl, ZrCH3 and Zr-other ligand (e.g. Cp or Biph-2-Indene) bonds as well as ligand specific signals were identified using literature data, model compounds and ab-initio quantum chemical calculations of the vibrational spectra. An excellent correlation was found between the intensity ratio of the peaks at 3000 and 1500 cm−1 and the Al/Zr ratio. A fairly linear correlation was found between the signal intensity due to MCH3 bonds and the catalytic yield (kg PE per mmole Zr) for a series of samples of different Al/Zr ratios and different catalytic yields.