DEVELOPMENT OF HIGH-PERFORMANCE, PD-BASED, 3 WAY CATALYSTS

The use of Pd in three-way catalytic (TWC) converters of automobiles p resents serious limitations which are related to sintering, poisoning and excessive selectivity for HC and CO oxidation, making NOx reductio n difficult. In the present work, an advanced automotive exhaust catal yst design is applied which reduces, to a large extent, these shortcom ings of Pd. This catalyst is based on dispersion of Pd on YSZ (ZrO2 st abilized with 8 mol-% Y2O3) forming the internal layer of a three-laye r washcoat. The external layers contain small quantities of Pt and Ph dispersed on suitable supports, such as gamma-Al2O3 and W6+-doped TiO2 , respectively. This scheme offers a high performance TWC with low lig ht-off temperature for the conversion of all three pollutants (GO, HC and NOx), enhanced poisoning tolerance and improved thermal resistance .