Silica-supported bimetallic catalysts were prepared by decomposing the molecular clusters Pt2Au4(C triple bond CtBu)8 and Pt2Cu4(C triple bond CtBu)8. The resulting catalysts were characterized with hydrogen, oxygen, and carbon monoxide chemisorptions. These indicated that CO chemisorption is the preferred method for evaluating metal dispersion. Chemisorption results also suggested that different types of substrate binding sites may be present on the bimetallic particles and that a significant fraction of the available platinum atoms may not be capable of activating hydrogen. Catalytic activity was evaluated with the toluene hydrogenation reaction. The new catalysts were found to be relatively inactive for this reaction at 60°C, despite having high platinum dispersions. Apparent activation energies for toluene hydrogenation were evaluated with Arrhenius plots. Although activities were low at 60°C, the cluster-derived catalysts had smaller apparent activation energies than a traditionally prepared Pt/silica catalyst. Trends in hydrogen chemisorption and toluene hydrogenation are discussed in terms of possible electronic, particle size, and ensemble size effects.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry