Abstract
The use of Pd in three-way catalytic (TWC) converters of automobiles presents serious limitations which are related to sintering, poisoning and excessive selectivity for HC and CO oxidation, making NO x reduction difficult. In the present work, an advanced automotive exhaust catalyst design is applied which reduces, to a large extent, these shortcomings of Pd. This catalyst is based on dispersion of Pd on YSZ (ZrO 2 stabilized with 8 mol-% Y 2O 3) forming the internal layer of a three-layer washcoat. The external layers contain small quantities of Pt and Rh dispersed on suitable supports, such as γ-Al 2O 3 and W 6+-doped TiO 2, respectively. This scheme offers a high performance TWC with low light-off temperature for the conversion of all three pollutants (CO, HC and NO x), enhanced poisoning tolerance and improved thermal resistance.
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