Quantitative relationship between the nature of surface species and the catalytic activity of tungsten oxides supported on crystallized titania

35-2 FIELD Section Title:Chemistry of Synthetic High Polymers 45, 67 Laboratoire Catalyse et Spectrochimie, ENSICAEN, CNRS, Universite de Caen, Caen, Fr. FIELD URL: written in EnglishA series of WOx/TiO2 catalysts contg. between 0.6 and 3.4 W at./nm2 was prepd. by pore vol. impregnation using ammonium metatungstate soln. on crystd. TiO2. Characterization of the solids by X-ray diffraction and Raman and IR spectroscopy indicated that the W phase was present essentially as a surface W species. The results also suggested an increased degree of condensation of the W phase with increasing W surface d. The most condensed W species was characterized by a ?(W=O) vibration at 1017 cm-1. The IR or Raman bands attributed to sp. surface species of the solids were correlated with the abundance of relatively strong Bronsted acid sites and isopropanol dehydration activity. A direct correlation was obsd. between propene formation rate and the area of the band at 1017 cm-1, attributed to the most condensed W species. Furthermore, the abundance of this species appeared to be directly related to that of Bronsted acid sites capable of retaining lutidine following desorption at 573 K. The behavior of the WOx/TiO2 system was compared with that reported for the corresponding WOx/ZrO2 solids. Higher intrinsic activity (activity per W atom) was obsd. for WOx/TiO2 system. [on SciFinder(R)