| abstract |
PROBLEM TO BE SOLVED: To provide a structure for selectively reducing nitrogen oxides contained in a lean exhaust gas stream of an internal combustion engine with ammonia using a compound which can be hydrolyzed to ammonia. To provide a catalyst. The catalyst has a reduction catalyst for selectively reducing nitrogen oxides with ammonia, and a hydrolysis catalyst for hydrolyzing a compound that can be hydrolyzed to ammonia. Here, the hydrolysis catalyst is applied on the reduction catalyst in the form of a coating. The structure length can be smaller than that of the conventional system, and furthermore, it has substantially more advantageous thermal characteristics. |