Method for reducing the nitrogen oxide concentration in gases

A method for reducing the content of N2O and NOx in gases, comprising:

• a) passing the N2O- and NOx-containing gas over two catalyst beds, wherein the first catalyst bed contains a catalyst for decomposing N2O into nitrogen and oxygen and the second catalyst bed contains a catalyst for chemically reacting N2O and NOx with a reducing agent;
• b) selecting temperature, pressure, and space velocity in said first catalyst bed so that the decrease of N2O content of the gas is not more than 95%, based on the N2O content of the gas at the entrance of said first catalyst bed, and
• c) adding a reducing agent for N2O and a reducing agent for NOx between the first and second catalyst beds in an amount sufficient to chemically remove all of the NOx and at least 50% of the N2O, based on the N2O content of the gas at the entrance of said second catalyst bed.