Structured catalysts for selective reduction of nitrogen oxides by ammonia using a compound that can be hydrolyzed to ammonia

A structured catalyst for selective reduction of nitrogen oxides contained in the lean exhaust gas of a combustion engine by ammonia using a compound that can be hydrolyzed to ammonia, which is injected into the exhaust gas stream in the form of an aerosol, comprising:

• a monolithic catalyst body, having a plurality of flow paths for the exhaust gas from an inlet face to an outlet face of said monolithic catalyst body, wherein the flow paths are formed by parallel channels regularly arranged over a cross section of the catalyst body and bounded by channel walls;
• said monolithic catalyst body containing a reduction catalyst for selective reduction of nitrogen oxides by means of ammonia and a hydrolysis catalyst for hydrolysis of the compound that can be hydrolyzed to ammonia, wherein said reduction catalyst:
• (i) is an extruded complete catalyst and forms the monolithic catalyst body and the hydrolysis catalyst is applied as a coating on said channel walls;
• or,
• (ii) said monolithic catalyst body is formed by an inert honeycomb body and the reduction catalyst and hydrolysis catalyst are applied as superimposed coatings onto the channel walls of the catalyst body with the reduction catalyst being the first layer on the channel walls and the hydrolysis catalyst lying on the reduction catalyst as the second layer.