Abstract: The relationship between aggregative MoO₃ and total MoO₃ loading in MoO₃/γ-Al₂O₃, MoO₃/TiO₂ and MoO₃/SiO₂ was determined by LRS. KNO₃ was used as the internal standard for the measurement of intensities. The obtained monolayer dispersion capacities by extrapolation correspond to those obtained by XPS, XRDand surface acidity measurement.Raman spectrometry can be used to indentify all molybdenum oxide species, for example the aggregative MoO₃ fine particles, Al₂(MoO₄)₃ and two dimensional Mo interaction species (monolayer dispersed MoO₃). So this result is a direct and convincible evidence for the view of monolayer dispersion. Some informations about the structure of catalysts supporting MoO₃ have been obtained by LRS, which was not obtained by XPS, XRD. The trouble in the quantitative LRSdetermination for catalysts, its cause and the method to overcome it are also discussed.

Key words: Laser Raman Spectra, LRS quantitative determination, Supported MoO₃ catalysts, Mono- layer dispersion capacity