AbstractTo study the effect of H2O2on NO reduction with NH3, the homogeneous gas phase reaction of NH3NOH2O2O2was investigated in a Pyrex flow reactor over the temperature range from 500°C to 600°C under one atmospheric pressure. H2O2accelerated the NO reduction by NH3and caused it to be induced at a temperature of 500°C. In the absence of O2, NOx reduction ratio of more than 90% was obtained for NH3/NO5 and H2O2/NO1 at 550°C. In the presence of O2or an excess of H2O2, two side reactions, which cause the NOx reduction ratio to decrease, occur.One of the side reactions is NO oxidation with H2O2. It was found experimentally that NO2inhibited NO reduction and that H2O2was an NO oxidizing agent, as well as an NH3decomposing agent. The other side reaction was the formation of NO and NO2, which resulted from the oxidation of NH3with O2. Under the conditions of our experiments, the amount of O2in our reaction system was extremely high compared to the amounts of NO, NH3and H2O2in the system. Thus NOxwas assumed to be produced by the oxidation of the NO reducing radicals, which were produced by the reaction of