CATALYST UNIT FOR REDUCTION OF NOX-COMPOUNDS

摘要

The invention consists of a catalyst unit (1;1') which is intended for reduction of NOx compounds in a gas stream and which comprises a catalytically active material of the silver/alumina type. The invention is characterized in that the catalyst unit (1;1') comprises at least one first reaction zone (3a, 3b, 3c, 3d, 3e) containing the said catalytically active material and at least one second reaction zone (4a, 4b, 4c, 4d, 4e; 8a, 8b, 8c, 8d, 8e) which is arranged to permit breakdown of a gas species which is formed in the said first reaction zone (3a, 3b,, 3c, 3d, 3e), with N2 being formed, and in that the gas stream is conducted through the first reaction zone (3a, 3b, 3c, 3d, 3e) and the second reaction zone (4a, 4b, 4c, 4d, 4e; 8a, 8b, 8c, 8d, 8e). The invention results in an improved catalyst unit which in particular provides high-grade reduction of NOx compounds in an exhaust gas stream from a combustion engine.