| abstract |
A catalyst coating or an extruded-type substrate monolith comprising a zeolite catalyst for converting nitrogen oxides in a gas to nitrogen by contacting the nitrogen oxides with a nitrogenous reducing agent in the presence of the zeolite catalyst, which zeolite catalyst comprising a combination of two or more small pore zeolites containing a maximum ring size of eight tetrahedral atoms and having the CHA Framework Type Code and containing a total of from 0.01 to 20 weight percent of at least one transition metal selected from the group consisting of Cr, Mn, Fe, Co, Ce, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Ag, In, Sn, Re, Ir and Pt, based on the total weight of the zeolite catalyst. |