Appeal No. 95-4932
Application No. 07/990,216
internal combustion engine operating under conditions where
oxygen is present in excess of the stoichiometric quantity.
Claims 1 and 4, the sole independent claims on appeal, are
representative:
1. A multicomponent catalyst for removing carbon
monoxide, hydrocarbons, and nitrogen oxides from the exhaust
gases of a lean burn internal combustion engine operating with
an air-fuel ratio above about 18/1 comprising at least two
components, each of said components characterized by being
able to reduce nitrogen oxides within a temperature range
beginning near the onset of activity for oxidation of the
carbon monoxide, hydrocarbons, and hydrogen by oxygen and
ending at a higher temperature, said components being disposed
in reverse order of their temperature range for nitrogen
oxides reduction so that the component which reduces nitrogen
oxides at the highest temperature range is exposed first to
the exhaust gases and with the component which reduces
nitrogen oxides at the lowest temperature range being exposed
last to the exhaust gases.
4. A multicomponent catalyst for removing carbon
monoxide, hydrocarbons, and nitrogen oxides from the exhaust
gases of an internal combustion engine containing oxygen in
excess of the stoichiometric quantity needed for complete
combustion comprising at least three components exposed in
sequence to the exhaust gases;
(a) a first component capable of reducing nitrogen
oxides at temperatures above about 475<C and up to about 800<C;
(b) a second component capable of reducing nitrogen
oxides at temperatures above about 315<C and up to about 475<C,
and
(c) a third component capable of reducing nitrogen
oxides to the diatomic elements at temperatures above about
200<C and up to about 425<C.
2
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Last modified: November 3, 2007