A SEM-EDS STUDY OF NEW AND USED AUTOMOTIVE CATALYSTS

Automotive catalyst deactivation by inorganic contaminants originating in engine oil and fuel is discussed. Scanning electron microscopy ima ges and energy dispersive spectroscopy analysis were used to character ize the variation of contaminant relative concentrations in various ty pes of used monolithic catalysts. The major contaminants were calcium, phosphorus, sulphur, lead, iron and zinc. All contaminants seems to h ave a cumulative time dependent effect, acting more as foulants than a s poisons. Valuable information about the washcoat composition were de rived. A preliminary acetic acid leaching test showed that a significa nt quantity of the contaminants may be easily removed from the catalys t surface.