HYDROGEN CHEMISORPTION ON 3-WAY AUTOMOTIV E CATALYSTS

Temperature-programmed desorption (TPD) is used to determine the exper imental conditions needed to characterize the dispersion of noble meta ls by hydrogen chemisorption on three-way exhaust-gas catalysts, It is shown that hydrogen chemisorption is activated on the samples. An ads orption temperature of 100-200-degrees-C must be used in order to obta in fast saturation of the sites. Under these conditions, the noble met al support chemisorbs H-2 as well. Only the TPD method permits the two sites of adsorption to be distinguished. For the various fresh indust rial catalysts studied, the metal dispersion is 100% using a ratio H/m etal = 1.