Structural Characterization of WO3/ZrO2 Catalysts using HAADF Imaging

Tungsten oxide supported on ZrO2 is receiving increased attention as a solid acid catalyst due to its important industrial applications, such as the isomerization of C4-C8 alkanes to upgrade gasoline octane number. It is known that the catalytic activity depends on the structure of WOx species and their interaction with ZrO2 support [1], so a thorough structural characterization is essential for establishing any structure-property relationships. Previous studies using a combination of XRD, optical spectroscopy and HRTEM revealed that WOx at low loadings is highly dispersed on ZrO2 as mono-tungstate or poly-tungstate species (Figure 1). Additional disordered WOx clusters appear on samples having intermediate WO3 loadings, which correlate with improved catalytic activity [2]. To date, however, no direct imaging studies of WOx configuration or their interaction with the ZrO2 support, which are important factors for catalytic activity, have been documented.