Noncatalytic Reduction of Nitrogen Monoxide with Ammonia and Oxidation of Ammonia with Oxygen

Abstract

The reduction of NO with NH₃ and oxidation of NH₃ with 02 were studied, in order to estabilish the relations among gas composition, temperature, residence time, fractional conversion of NO, and the reaction mechanism in noncatalytic reduction of NO with NH₃. The experiments were carried out by using a flow reactor under an atmospheric pressure and at 750-4100°C. The composition of the inlet gas was mainly 0-4500 ppm NO-500-4500 ppm NH₃-0-5% 02-0, 10% H₂O-N2 and the residence time was 0.37, --3.4 Nsec. The following results were obtained: (1) The higher the temperature up to ca.1000°C, the longer was the residence time, and the larger the inlet mole ratio of NI-la/NO, the higher became the fractional conversion of NO. (2) The apparent stoichiometric reaction equation was given as follows: NO+NH₃+ (1/4)02N2+ (3/2)H₂0. (3) For the purpose of obtaining Ca.100% of fractional conversion of NO, it was required that the inlet mole ratio of NH, /NO was ca.3, and the residence time was above 1.5 Nsec at ca.1000°C. (4) It was deduced that when the formation rate of NH radical, an intermediate species in oxidation of NH₃ with 02, exceeded a certain value, NO was reduced to N2 according to the reactions NH⁺02 N0+ OH and NO+NH N2+ OH, and that the reactions of NI-13+0H NH, +H₂0 and NH₂+0H--NH⁺H₂0 occurred. In such a way, the chain reaction proceeded in terms of OH radical which behaved as a carrier.