The Nature of Active Sites in the Pd/C-Catalyzed Hydrogenation/Hydrodeoxygenation of Benzaldehyde

Hydrogenations and hydrodeoxygenations represent two of the most important reactions in the production of both bulk and fine chemicals. Despite the wide and long use of metal-based catalysts for this reaction, there is still some uncertainty with respect to the properties governing the catalyst activity. Using the hydrogenation of benzaldehyde as a model reaction, in this paper, we disclose the dominant parameters determining catalyst activity of Pd nanoparticles supported on a carbonaceous material (carbon nanoplates, GNP). In particular, several operating parameters of the catalyst synthesis were varied in order to obtain materials with differences in such physico-chemical properties as nanoparticle size, Pd oxidation state and Pd surface exposure. A linear correlation between catalyst activity and the amount of surface Pd(0) atoms was found; this dependence, maintained after catalyst recycling, pointed out the nature of the active site of the Pd/GNP catalyst represented by exposed Pd(0) species.