(675a) Dendrimer-Derived Bimetallic Catalysts for Liquid-Phase Hydrogenation Reactions

Bimetallic catalysts prepared by conventional synthetic methods often result in wide particle size distributions and non-uniform materials that can be difficult to characterize on a fundamental level. Dendrimer-metal nanocomposites (DMNs) provide novel synthetic routes that can be applied to produce heterogeneous catalysts. The use of DMN precursors for supported catalysts has demonstrated control of metal nanoparticle size and composition even after thermal removal of the dendrimer ?shell?. Supported bimetallic catalysts possess unique properties that can enhance activity and selectivity for a variety of reactions. In this work we will report on the preparation and characterization of supported bimetallic catalysts via the DMN approach, focusing specifically on the Pt-Ru and Ir-Pd systems. These catalysts have been characterized using a range of techniques, including HRTEM/STEM/EDX, FTIR spectroscopy, TPR/TPO, and XRD. The results show that DMN-derived bimetallic precursors can form different nanoparticle sizes, distributions, and compositions than for catalysts prepared by conventional methods such as incipient wetness or wet impregnation. These catalysts have been evaluated for liquid-phase hydrogenation reactions with notable differences observed depending on the preparation method. For example, benzonitrile hydrogenation kinetic studies on Ir-Pd catalysts show differences in activity and selectivity towards primary versus secondary amines. In the case of Pt-Ru catalysts, the activity for epoxy butene hydrogenation is greatly enhanced due to the enhanced presence of highly active Pt-Ru sites in dendrimer-derived catalysts. The future prospects and hurdles of the DMN approach for producing novel bimetallic catalysts will be discussed.