Catalytic activity of dispersed CuO phases towards nitrogen oxides (N2O, NO, and NO2)

A systematic reactivity study of N2O, NO, and NO2 on highly dispersed CuO phases over modified silica supports (SiO2–Al2O3, SiO2–TiO2, and SiO2–ZrO2) has been performed. Different reaction paths for the nitrogen oxide species abatement were studied: from direct decomposition (N2O) to selective reductions by hydrocarbons (N2O, NO, and NO2) and oxidation (NO to NO2). The oxygen concentration, temperature, and contact time, were varied within suitable ranges in order to investigate the activity and in particular the selectivity in the different reactions studied. The support deeply influenced the catalytic properties of the active copper phase. The most acidic supports, SiO2–Al2O3 and SiO2–ZrO2, led to a better activity and selectivity of CuO for the reactions of N2O, NO, and NO2 reductions and N2O decomposition than SiO2–TiO2. The catalytic results are discussed in terms of actual turnover frequencies starting from the knowledge of the copper dispersion values.