EFFECTS OF THE SURFACE-STRUCTURE OF RH-GAMMA-AL2O3 ON THE HYDROGENOLYSIS OF N-PENTANE, ON THE OXIDATION OF N-BUTANE, AND ON THE REDUCTION OF NITRIC-OXIDE

In low-concentration Rh catalysts, supported on γ-Al2O3, the metal is present in a dispersed phase with every Rh atom or ion exposed on the surface. This form persists up to a surface concentration of 2.5 μmol/m2 (BET). At higher concentrations three-dimensional particles are formed. Three model reactions were investigated on Rh catalysts of both kinds: hydrogenolysis of n-pentane under strongly reducing conditions, oxidation of n-butane under strongly oxidizing conditions, and reduction of nitric oxide by hydrogen under mildly oxidizing conditions. The n-butane oxidation proceeded in the same fashion on both types of Rh catalysts, while the two other reactions were found to be structure sensitive. On the dispersed phase, n-pentane cleaves predominantly into ethane and propane, while on the three-dimensional particles this activity is sharply diminished. Similarly, the product selectivity and the kinetic parameters of the NO-H2 reaction differ distinctly on the two phases of supported Rh. © 1979.