Bimetallic NiAu catalysts have garnered broad interest for various reactions including selective hydrogenations and selective oxidations. However, studies of this bimetallic system have been limited due to the bulk immiscibility of the two metals that makes catalyst synthesis a challenge. Our group has developed a solution phase synthesis using oleylamine-capped Ni nanoparticles that are formed using a colloid method. The optimized Ni synthesis led to particles with a narrow size distribution (4.7 ± 0.4 nm). Gold was added to the Ni nanoparticles via galvanic displacement before they are deposited onto a commercial alumina to yield new bimetallic heterogeneous catalysts. While this process yielded bimetallic nanocomposites, large particle size growth and the production of small Au particles was also observed. The supported NiAu catalysts were more active than Au for 1-octyne partial hydrogenation, and largely maintained the high alkene selectivity associated with Au catalysts (90% alkene selectivity at 95% conversion). When operated at lower space velocities, the NiAu catalysts also had reduced propensity to over-hydrogenate the alkene, allowing for wider operating ranges with high alkene yields when compared to Ni catalysts alone. Stability testing showed the bimetallic catalyst activity increased significantly over the first ~15 hours on stream and remained stable for one week. In control experiments, NiAu catalyst performance was compared with reactivity over Au/NiO and with physical mixtures of Au/Al2O3 and Ni/Al2O3 catalysts. Only the NiAu catalysts prepared through the colloid synthesis showed the enhanced activity and selectivity. The reactivity and characterization studies suggest that the active catalysts are likely composed of bimetallic NiAu particles that have heavily enriched Au surfaces.

Supported Ni-Au colloid precursors for active, selective, and stable alkyne partial hydrogenation catalysts

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.