Determination of the surface coverage of WO3/TiO2 catalysts by CO2 chemisorption

The surface coverage of a series of WO3/TiO2 catalysts prepared by incipient wetness impregnation was monitored by CO2 chemisorption. The coverage of the TiO2 support increases from 31+/-2% for the 3.3 wt% WO3/TiO2 catalyst to ca. 86+/-2% for catalysts with loadings greater than or equal to 10.3 wt% WO3. The leveling off of the surface coverage for the high-loading catalysts has been attributed to the formation of W multilayers or bulk WO3. The surface coverage values obtained by CO2 chemisorption were consistent with those measured previously using ion scattering spectroscopy. The apparent suitability of CO2 chemisorption for monitoring the surface coverage of TiO2-supported catalyst systems, in contrast to previous results for Al2O3-supported systems, will be discussed.