C-NO reaction in the presence of O2

The reactions of NO with pure carbons, phenol-formaldehyde resin char and amorphous C-13, were examined at 850 degrees C in the presence of O-2. Previous studies revealed that some of the nitrogen in NO was trapped on the carbon surface, and it plays an important role in the C-NO reaction. In order to quantitatively investigate the formation and removal of N-containing complexes on the carbon surface, C(N), in the presence of O-2, a detailed material balance in the course of NO reduction over the carbons, was established by using both mass spectrometer and gas chromatography. The presence of O-2 greatly enhanced the NO reduction rate. It was found that the N-2 and N2O production rates increased, whereas the accumulation of C(N) considerably decreased with increasing O-2 concentration. The C-NO reaction mechanism in the presence of O-2 was examined by step response experiments at 850 degrees C, where the reactant gas was switched from (NO)-N-14-O-16/O-16(2) to (NO)-N-15-O-18/O-18(2). Analysis of the product gases after the feed gas switch gives much information on the reaction pathways. It was suggested that the most dominant N-2 formation route is the reaction between C(N) and NO gas under the present conditions. This mechanism is the same as observed previously in the absence of O-2 The reaction of C(N) with O-2 at 850 degrees C was also carried out, and the principal product was found to be N-2 in the early stage and NO in the later stage. As one of the possible roles of O-2 on the NO reduction by carbon, the increase of C(N) turnover by the action of O-2 was suggested; that is, O-2 assists the liberation of C(N) from the carbon surface to produce gaseous products.