Effects of Ce/Zr ratio on the reducibility, adsorption and catalytic activity of CuO/CexZr1−xO2/γ-Al2O3 catalysts for NO reduction by CO

Abstract

Effects of Ce/Zr ratio on the physicochemical properties of CuO/CexZr1−xO2/γ-Al2O3 catalysts were investigated by BET, XRD, Raman and H2-TPR. The catalytic activity and the interaction between the reactants with these catalysts were compared by NO+CO model reaction and in situ FT-IR. The results suggested that the addition of ceria–zirconia mixed oxides significantly improved NO conversion and N2 yield due to dispersed copper species in proximity to ceria–zirconia. Especially, the ceria-rich catalysts displayed better performance in activity and reducibility than others, which would be resulted from the strong interaction among copper, ceria–zirconia and support. The IR results suggested NO reduction activity was correlated with the presence of Cu+ carbonyl species, and the catalysts with variable Ce/Zr ratios had no distinction at the adsorption type and rate of NO/CO at room temperature. However, on heating treatment would give distinct difference in CO2 intensity and the wavenumber of adsorbed nitrates. Simultaneously, the stability of these N- and C-containing intermediates contacted with alumina was influenced by the modified Ce/Zr ratio.