Die Raman‐Spektren von MoO3/Al2O3‐Katalysatoren mit 3‐25 Gew.‐% MoO3 werden vom H2O‐Gehalt der Proben dramatisch beeinflußt. In O2 bei 500°C calcinierte Katalysatoren zeigen Spektren, die sich von früher veröffentlichten stark unterscheiden.

The Raman spectra of a series of WO3-AI2O3 catalysts containing 1-30 wt-% of W 0 3 were investigated with respect to the effect of Oz calcination and HzO-DzO exposure. These studies showed that the frequencies of bands due to surface tungstate species can be shifted reversibly by as much as 6% of their values during alternate O2 calcination and HzO exposure cycles. The exchange of "0 for l60 in the surface tungstate was also investigated with Raman spectroscopy and ion-scattering spectrometry. The results were used to assign Raman bands to fundamental vibrations of the surface tungstate and to propose a mechanism of interaction between H 2 0 and the surface tungstate that hitherto has not been addressed for WO3-AI2O3.

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