FTIR spectroscopic study of the nature and reactivity of NOx compounds formed on Cu/Al2O3 after coadsorption of NO and O2

Abstract Copper cations present on alumina surface even in low concentrations (0.75 wt %) are characterized by a high heterogeneity. Thus, two kinds of Cu + sites have monitored by CO adsorption and three kinds of Cu 2+ cations by NO adsorption. Adsorption of NO also leads to development of bands due to small amounts of nitro/nitrito and nitrato compounds. Introduction of oxygen to the Cu/Al 2 O 3 –NO system causes initial concentration rise of the NO 2 − compounds followed by oxidation of these complexes to nitrates. The nitrates thus obtained are stable up to 723 K. Surface copper nitrates begin to react with C 2 H 4 at 573 K, as a result of which isocyanate and cyanide species are formed. Simultaneously, oxidation of C 2 H 4 on the catalyst surface proceeds, leading ultimately to the appearance of carboxylates. The mechanism of SCR by ethene on Cu/Al 2 O 3 has been discussed.