Synthesis and Characterization of Cluster-Derived PtRu5Sn Catalysts

Magnesia-supported trimetallic Pt-Ru-Sn catalysts prepared through a cluster and a conventional synthetic route have been investigated in terms of their structural properties and their catalytic activity for the hydrogenation of citral. FTIR results indicate that the majority of the stabilizing ligands remain attached to the PtRu5(mu-SnPh2)(C)(CO)(15) cluster used following impregnation onto the MgO support. Under H-2 reduction conditions, partial and full ligand removal are observed at 473 and 573 K, respectively. HRSTEM analysis shows that cluster-derived samples exhibit significantly smaller average metal particle sizes, as well as narrower particle size distributions than the corresponding conventionally prepared ones. EDS measurements show that in the cluster-derived catalysts, the majority of the metal particles present are trimetallic in nature, with metal compositions similar to those of the original cluster. In contrast, the conventionally prepared materials contain mostly bimetallic and monometallic particles with variable compositions. The formation of smaller metal particles in the cluster-derived catalysts and the presence of the three metals in these particles in close proximity result in higher activity and selectivity for the hydrogenation of citral.