STUDIES OF THE SELECTIVE REDUCTION OF NITRIC-OXIDE BY HYDROCARBONS

The selective reduction of nitric oxide with isobutane in the presence and absence of oxygen has been studied over Cu-ZSM-5-14-114 and compa red to the simple decomposition reaction. In the presence of sufficien t oxygen, complete combustion of the hydrocarbon was observed, whereas in its absence, acid catalysis accompanied by dehydrogenation associa ted with coking occurred. The effect of adding nitric oxide to the HC/ He stream in the absence of oxygen was small; the conversion to nitrog en was little affected by the hydrocarbon. When oxygen was added, howe ver, the decomposition was complete at 573 K even at high space veloci ties (e.g., SVH approximately 10(4)) even though the combustion was no t. Isobutane (an alkane) was more effective than C3H6 (an alkene) for the selective reduction; this is not generally the case. The presence of excess oxygen inhibited aging of the catalyst.