Percentage of metal exposed on commercial three-way catalysts

A new sensitive method has been developed to determine the percentage of me tal exposed (% ME) in commercial three-way bimetallic catalysts, fresh and aged. The method is based on the measurement of specific rates of two struc ture insensitive reactions: the hydrogenation of benzene and propene. Value s of % ME were obtained for each metal at the surface of Pt-Ph and Pd-Rh ca talysts with very low % ME. The % ME and the corresponding catalytic activi ty of the samples in the postcombustion follow the same trend as a result o f aging.