CHARACTERIZATION OF TUNGSTA TITANIA CATALYSTS

The structural, morphological, and surface properties of a WO3-TiO2 catalyst (W = 6% (w/w)) have been investigated and compared with those of TiO2. X-ray diffraction, differential thermal analysis, porosity, and surface area measurements indicated that WO3 inhibits the initial sintering of anatase and its phase transformation to rutile. Fourier transform infrared spectra of adsorbed water, pyridine, ammonia and carbon dioxide show that WO3-TiO2 is a very strong Lewis acid, displays also a Bronsted acid behavior, and lacks significant surface basicity. Surface tungsten oxide species consist of wolframyl groups (W=O) that are coordinatively unsaturated on dry surfaces. The different properties of WO3-TiO2 and V2O5-TiO2 are discussed in relation to their use as catalysts for the selective catalytic reduction of NO(x).