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US 6,089,015 AGranted
Method of purifying a lean exhaust gas and catalytic system therefor
AssigneeDegussa-Huls AG
InventorsWolfgang Strehlau, Egbert Lox, Thomas Kreuzer, Jurgen Hohne
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Abstract
A method of purifying the lean exhaust gas of lean mix engines or diesel engines. The exhaust gas is first contacted with a permanent reduction catalyst and subsequently contacted with a nitrogen oxide storage catalyst. This procedure yields a uniformly good conversion of pollutants of the exhaust gases under differing operating conditions both as regards the air ratios and the exhaust gas temperatures.
Claims12
A method of purifying lean exhaust gas, from a lean mix engine or a diesel engine, containing hydrocarbons, carbon monoxide and nitrogen oxides, the method comprising;
- conducting said exhaust gas through a cold start, three-way pre-catalyst positioned close to the engine;
- thereafter conducting said exhaust gas through a permanent reduction catalyst, thereby reducing nitrogen oxides with the aid of hydrocarbons and carbon monoxide as reducing agents;
- and thereafter
- conducting said exhaust gas through a nitrogen oxides storage catalyst, to trap residual nitrogen oxides leaking from the permanent reduction catalyst.
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Dependencies are inferred from the claim text.