| Modified metal oxides are playing an increasingly important role as catalysts in the chemical and petrochemical industries. Dopants such as sulfate and tungstate alter a material's acidic properties and thus the performance in a catalytic application. Sol-gel chemistry provides a powerful means of controlling the interaction between a dopant and a host oxide such as zirconia. It allows investigation of the relationship between the structural properties of a material modified by dopants, and the associated acidic and catalytic properties--an approach not readily accessible by traditional preparation methods.; We investigated the influence of processes such as preparation method and activation temperature on the catalytically active species and the corresponding surface acidity of modified zirconia aerogels. Zirconia-tungstate activation for application in a reaction proved to be dependent on several variables including the method of preparation. We noted that the active species in an acid catalyzed reaction was the same regardless of preparative history, and demonstrated the necessity for correct activation before comparison with other materials. This study also provided a means for preparation to advance the understanding of the acidity. Our experience with zirconia-tungstate enabled the development of an acidity scale by which modified zirconia aerogels could be compared.; Using zirconia-tungstate as a basis, we explored the current understanding of the presence of extra dopants on zirconia-based materials. Sulfate, phosphate and silica were incorporated to zirconia-tungstate to study the effect of a second dopant distributed in, or promoted onto, a support. The flexibility of sol-gel chemistry allowed us to document the relationship between dopant loading, distribution and acidic properties. We illustrated the multidisciplinary nature of catalysis research and established the importance of material synthesis in understanding catalytic phenomena. |
