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The temperature programmed desorption (TPD) is used to determine the experimental conditions needed to characterize the dispersion of precious metals by hydrogen chemisorption on three way exhaust gas catalysts. It is shown that hydrogen chemisorption on the samples is activated. An adsorption temperature of 370-473 K must be used in order to obtain a fast saturation of the sites. In these conditions, the support of the precious metals chemisorbs H2 as well. Only the TPD method permits to distinguish the two sites of adsorption. For the various fresh industrial catalysts studied the metal dispersion is around 100 % using a ratio H/metal=1. The change of the hydrogen chemisorption with the thermal ageing of the catalysts under inert gas is studied.

The long-term durability of a ceramic racetrack converter is examined using the systems approach. Each of the converter components is characterized with respect to its behavior under simulated mechanical and thermal loads. In particular, the impact of three different washcoats on key physical properties, and the load vs. deformation characteristics of three different insulation mats are examined from mechanical and thermal durability point of view. Similarly, the can deformation at elevated temperature is taken into account to ensure adequate mounting pressure on ceramic monolith under all operating conditions. The temperature distribution at the midbed of the catalyst during engine dynamometer testing, together with the component properties data, are then used in a finite element model to compute thermal stresses in the monolith as function of engine load and speed.

A laboratory scale analytical procedure is described to determine the efficiency of three way exhaust gas catalysts (Pt/Rh/monolith) by F.T.I.R. spectroscopy. An extruded part of monolith was used to convert synthetic gas mixtures (CO/NO/Hydrocarbons/CO2/H2O/N2) which have compositions similar to motor vehicule exhaust gases. The catalyst efficiency was determined as a function of gas temperature and equivalent air-fuel ratio (with and without perturbation). F.T.I.R. spectroscopy appears as an alternative method compared to the present one using several specific detectors. Comparative data are obtained on the conversion of CO, NO and hydrocarbons. In addition F.T.I.R. spectroscopy was capable of giving the following informations: the conversion of each hydrocarbons (in case of mixture of hydrocarbons), the transient formation of N2O and the occurence of NO2.