Promotion of Supported Metal Nanoclusters

A similar model was proposed by Vannice et to explain the extremely high 

The enhanced selectivity of Ru/Zr02 toward cinnamyl alcohol in cinnamal-dehyde hydrogenation was also ascribed to the formation of Ru-Zr sites at the periphery of the nanoparticles. The presence of mixed Ru-Zr sites appeared to decrease the strength of the C=0 bond, thus facilitating the hydrogenation.  

Similar interfacial active sites created in Pt/MoOs and Pt/WOa upon high temperature reduction were suggested to favor the isomerization of allyl alcohol to propanal at the expense of hydrogenation to propanol.  

Bell and SomorjaP proposed the concept of the interfacial active site involving the coupling of a metal center and a Lewis acid/base site to form adjacent centers. The latter sites are formed either in the oxide support or the added promoter. It was suggested that these active sites might be crucial in the conversion of the molecules with polar functional groups (such as CN, CS and NH). Close analysis of data presented in the above references shows that in all cases the character of interactions strongly resembles the presence of metal ion-metal nanocluster ensemble sites. 

---