Intermediates in the reaction of NOx reduction with propane over Cu/ZSM-5 catalysts (by ESR, TPD, and IR-spectroscopy in situ)

On the base of ESR, TPD, and IR-spectroscopy in situ data, the Cu2+-O-N=O complex is found to be formed on the surface of Cu-containing zeolites in the reduction of NO by propane under oxygen excess. The spectrokinetic method was used to measure the rate of further conversion of this complex to the reaction products. It appeared to be equal to the reaction rate. Coincidence of these two rates implies that the Cu2+-O-N=O complex is a true intermediate in this reaction and takes part in the rate-determining stage. Cu-isol(2+) isol ions in the samples studied are the centers where one of the first stages of the reaction (NO activation) proceeds. The next stages occur, possibly, over other surface states of the copper. From this point of view, the Cu-isol(2+) ions is a necessary part of the complex active center of the reaction. (C) 1997 Academic Press.