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Thermal resistant automotive
(three way) catalysts were developed with particular
attention to oxide materials such as supports and
promoters.
Various analytical techniques were used to the study
of the catalytic materials subjected to durability
tests. The study revealed dominant causes for the
catalyst degradation under high temperatures, such
as sintering of precious metals, surface area reduction
of supports and deactivation of promoters. Modification
of alumina with small amount of rare earths resulted
in large improvement of thermal stability of catalyst
support. The study of promoters revealed that complex
oxides in cerium-zirconium-lanthanum systems was
useful in providing excellent oxygen storage components
in three way catalysts.
Catalyst design concept
is described for the development of catalysts suitable
for operations under thermally severe conditions
at above 900℃.
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