(678b) Hydrogen-Deuterium Exchange Over Ceria-Zirconia Mixed Metal Oxides

Ceria based supports are commonly used in supported metal catalysts. In many cases these supports are of interest because their redox properties facilitate reactions that are commonly attributed to the metal particle. However, ceria catalysts also have activity for reactions that are typically metal catalyzed, such as the hydrogenation of acetylene.

The present work shows that the ability of ceria to activate hydrogen is enhanced for ceria-zirconia mixed metal oxide catalysts. H₂/D₂ isotopic exchange is used to probe this ability. It is shown that there are different types of active sites with different activation energies for the exchange reaction. In-situ IR spectroscopy is used to identify these sites. Detailed physico-chemical characterization is performed to obtain structure-property relationships. Most importantly, it is shown that the H₂/D₂ exchange activity increases with decreases crystallite size of ceria-zirconia. In addition, the presence of defect sites from surface reduction of ceria-zirconia has a strong impact on the H₂/D₂ exchange reaction.

Correlations of H₂/D₂ exchange activity with catalytic performance in other reactions will be discussed.