NOx storage and reduction over copper-based catalysts. Part 2: Ce0.8M0.2Oδ supports (M = Zr, La, Ce, Pr or Nd)

5% copper catalysts with Ce0.8M0.2O delta supports (M = Zr, La, Ce, Pr or Nd) have been studied by rapid scan operando DRIFTS for NOx Storage and Reduction (NSR) with high frequency (30 s) CO, H-2 and 50%CO + 50%H-2 micropulses. In the absence of reductant pulses, below 200-250 degrees C NOx was stored on the catalysts as nitrite and nitro groups, and above this temperature nitrates were the main species identified. The thermal stability of the NOx species stored on the catalysts depended on the acid/basic character of the dopant (M more acidic = NOx stored less stable double right arrow Z(4+) < none < Nd3+ < Pr3+ < La3+ double left arrow M more basic = NOx stored more stable). Catalysts regeneration was more efficient with H-2 than with CO, and the CO + H-2 mixture presented an intermediate behavior, but with smaller differences among the series of catalyst than observed using CO alone. N-2 is the main NOx reduction product upon H-2 regeneration. The highest NOx removal in NSR experiments performed at 400 degrees C with CO+H-2 pulses was achieved with the catalyst with the most basic dopant (CuO/Ce0.8La0.2O delta) while the poorest performing catalyst was that with the most acidic dopant (CuO/Ce0.8Zr0.2O delta). The poor performance of CuO/Ce0.8Zr0.2O delta in NSR experiments with CO pulses was attributed to its lower oxidation capacity compared to the other catalysts. (C) 2016 Elsevier B.V. All rights reserved.