CHARACTERIZATION OF THE SURFACE-PROPERTIES OF POLYCRYSTALLINE WO3

Tungsten trioxide was precipitated from an ammonium paratungstate aqueous solution at acid pH. The precipitated material consists of a mixture of hexagonal and pseudocubic WO3. After calcination at about 700 K, it transforms into monophasic pseudocubic WO3 (15m2 g-2). FTIR investigation of adsorbed water, ammonia, pyridine, pivalonitrile and CO2 indicates an acid nature of the surface. Two types of strong Lewis acid sites, as well as Brönsted acid sites, have been detected. Models are proposed for the surface sites of WO3, and the catalytic activity of WO3-containing catalysts is briefly discussed in relation to their surface chemistry. © 1990.