Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Silicon containing or process of making
Reexamination Certificate
2001-05-01
2004-11-09
Silverman, Stanley S. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Silicon containing or process of making
C502S250000, C502S251000
Reexamination Certificate
active
06815393
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a catalyst for purification of exhaust gas, containing an alkali metal and/or an alkaline earth metal as an NO
x
-adsorbing component, particularly a catalyst for purification of an exhaust gas emitted from an internal combustion engine of gasoline vehicle, diesel vehicle or the like.
(2) Description of Related Art
In recent years, regulation for exhaust gas has become stricter, and lean burn engines, direct injection engines, etc. have come into wide use. In this connection, NO
x
-adsorbing catalysts capable of effectively purifying the NO
x
present in ah exhaust gas, in a lean atmosphere have been put into practical use. As the NO
x
-adsorbing component used in the NO
x
-adsorbing catalyst, there are known alkali metals such as K, Na, Li, Cs and the like; alkaline earth metals such as Ba, Ca and the like; and rare earth elements such as La, Y and the like. Recently, it has been attempted to use, in particular, K which is superior in NO
x
adsorption at high temperatures.
NO
x
-adsorbing catalysts are generally constituted by loading a catalyst layer containing the above-mentioned NO
x
-adsorbing component, on a carrier composed of an oxide type ceramic (e.g. cordierite) or a metallic material (e.g. Fe—Cr—Al alloy). Such a carrier, however, has a problem; that is, it is easily corroded and deteriorated by alkali metals or part of alkaline earth metals, particularly, Li, Na, K and Ca when they become active under the high temperatures of exhaust gas.
SUMMARY OF THE INVENTION
In view of the above problem of the prior art, the present invention aims at providing a catalyst for purification of exhaust gas, obtained by loading, on a carrier, a catalyst layer containing an alkali metal and/or an alkaline earth metal as an NO
x
-adsorbing component, which catalyst can suppress the deterioration of the carrier caused by the alkali metal and/or the alkaline earth metal and therefore can be used over a long period of time.
According to the present invention, there is provided a catalyst for purification of exhaust gas comprising: a carrier, and a catalyst layer containing an alkali metal and/or an alkaline earth metal, the catalyst layer being loaded on the carrier, in which catalyst the carrier-composing material contains Si in an amount of 0.5 to 10.0% by weight as expressed as an oxide.
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Noda Naomi
Suzuki Junichi
Johnson Edward M.
NGK Insulators Ltd.
Parkhurst & Wendel L.L.P.
Silverman Stanley S.
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