EXHAUST EMISSION CONTROL DEVICE FOR ENGINE

摘要

PROBLEM TO BE SOLVED: To improve NOx conversion rate in the transition period while effectively using reducer or its precursor.

SOLUTION: Reducer adsorption layer 20B temporarily adsorbing reducer at temperature lower than catalyst activation temperature, and selective reduction layer 20C supplied with reducer and converting NOx by selective reduction reaction are applied on a catalyst carrier 20A arranged in an exhaust gas passage plurality of times alternately in this order from an exhaust gas upstream to a downstream, and reducer adsorption layers 20B are arranged in such a manner that reducer adsorption capacity of each reducer adsorption layer 20B gets lower as it goes from the exhaust gas upstream to the downstream. Reducer is adsorbed by the reducer adsorption layer 20B at temperature lower than catalyst activation temperature and NOx is reduced by using reducer desorbed from the reducer adsorption layer 20B at temperature not less than the catalyst activation temperature. Consequently, shortage of reducer during transient period can be avoided while reducing reducer discharged to atmosphere.

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