Volcano-curves for dehydrogenation of 2-propanol and hydrogenation of nitrobenzene by SiO ₂-supported metal nanoparticles catalysts as described in terms of a d-band model

To confirm whether the activity trends in multistep organic reactions can be understood in terms of the Hammer-Nørskov d-band model in combination with the linear energy relations, we studied correlations between the reaction rates for dehydrogenation and hydrogenation reactions and the position of the d-band center (ε _d) relative to the Fermi energy (E _F), the ε _d - E _F value, of various metal catalysts. SiO ₂-supported metal (M = Ag, Cu, Pt, Ir, Pd, Rh, Ru, Ni, and Co) catalysts with the same metal loading (5 wt %) and similar metal particle size (8.9-11.7 nm) were prepared. The dehydrogenation of adsorbed 2-propanol in a flow of He and the hydrogenation of adsorbed nitrobenzene in a flow of H ₂ were tested as model reactions of organic reactions on the metal surface. As a test reaction of H ₂ dissociation on the surface, SiOH/SiOD exchange on the M/SiO ₂ catalysts in a flow of D ₂ is carried out. The liquid phase hydrogenation of nitrobenzene under 3.0 MPa of H ₂ is adopted as an organic reaction under realistic conditions. Generally, the activities show volcano-type dependences on the ε _d - E _F value, indicating that the ε _d - E _F value is useful as a qualitative activity descriptor in heterogeneous catalysis of metal nanoparticles for multistep organic reactions.