Reactant-Probe Method for Estimating Active Site Number in Catalysts

The number of surface sites on catalysts can be measured by well-established chemisorption techniques employing small molecules or by a reactant-probe method utilizing the actual reacting species in a catalytic reaction. The latter approach gives the advantage of directly titrating the actual reactive sites on the surface and has been demonstrated in a number of systems. An example is given for the case of manganese oxide supported on SiO2, Al2O3, TiO2, and ZrO2, which are good catalysts for the decomposition of ozone. Reasonable correspondence is found between oxygen chemisorption and temperature-programmed desorption of adsorbed ozone species, but the latter is better able to account for dual sites found on the ZrO2 support.