Abstract: A reactor for the catalytic oxidation of ammonia to form nitrogen oxides which has a noble metal gauze catalyst and a heat exchanger in that order in the direction of flow, a catalyst for the decomposition of N2O is located between the noble metal gauze catalyst and the heat exchanger and in a process for the catalytic decomposition of N2O in a gas mixture obtained in the preparation of nitric acid by catalytic oxidation of ammonia, where the N2O is decomposed catalytically over a catalyst of the decomposition of N2O, the hot gas mixture obtained from the catalytic oxidation of ammonia is brought to contact with the catalyst for the decomposition of N2O prior to subsequent cooling.

Abstract: A copper-containing catalyst of the composition of N2O contains a compound of the formula MxAl2O4, where M is Cu or a mixture of Cu and Zn and/or Mg and x is from 0.8 to 1.5. The novel catalyst is used in a process for the catalytic decomposition of pure N2O or N2O contained in gas mixtures, at elevated temperatures.

Abstract: The invention relates to a process for removing nitrogen oxides from a gas stream containing same, which comprises passing the gas stream(A) through a stage for absorbing the nitrogen oxides other than N.sub.2 O in an absorbent or reacting the nitrogen oxides other than N.sub.2 O with an absorbent at a pressure of from 1,5 to 20 bar, and(B) through a stage for reducing the amount of N.sub.2 O, preferably employing the pressure level of step A, and to apparatus therefor and the use thereof.