Highly Active Large Au Clusters and Even More Active Ag Nanoparticles Supported on Ceria-Zirconia: Impact of Particle Size and Potassium Ion Loading on Activity in Catalytic Transfer Hydrogenation

• Published in: Catalysts 2022-09, Vol.12 (9), p.974
• Main Authors: Iwanek (nee Wilczkowska), Ewa M., Gliński, Marek, Siwiec, Aleksandra, Siennicka, Sylwia, Zybert, Magdalena, Kaszkur, Zbigniew
• Format: Article
• Language: English
• Subjects: Acetophenone; Catalysts; Catalytic activity; Catalytic oxidation; catalytic transfer hydrogenation; ceria-zirconia; Cerium; Cerium oxides; Chemical reactions; Gold; Hydrogen; Hydrogenation; large gold particles; Liquid phases; Nanoparticles; Particle size; Potassium; Potassium carbonate; potassium ion doping; Selectivity; Silver; silver nanoparticles; Solid solutions; VOCs; Volatile organic compounds; Zirconium; Zirconium dioxide; Zirconium oxide
• ISSN: 2073-4344; 2073-4344
• DOI: 10.3390/catal12090974

Although heterogeneous monometallic gold catalysts are commonly more active when the gold particles are smaller, this study shows that the reverse is true in the case of liquid phase catalytic transfer hydrogenation of acetophenone with 2-pentanol. Higher catalytic activity of larger gold particles, i.e., over 30 nm in diameter, than of smaller particles of average 4 nm in size was observed. Moreover, this effect was contradictory to that observed for supported monometallic silver catalysts in which the interaction with the support and hence particle size was shown to cause drastic changes in the activity in this reaction, with the large particles being completely inactive and tiny ones being the most active system studied. In this reaction, the ceria-zirconia solid solutions were used as the supports for the catalysts and both zirconium doped ceria, as well as cerium doped zirconia carriers were tested. The supports themselves exhibited little activity in this reaction. It was shown that the activity of the supports and catalysts depends on the Ce/Zr ratio and potassium content. Both types of catalysts showed excellent selectivity to 1-phenylethanol and conversion of acetophenone, although it was noted that a high loading of potassium carbonate in the gold catalysts propelled undesired reactions, thereby reducing the selectivity to 1-phenylethanol.