Effect of a ZrO2 support on Cu/Fe2O3–CeO2/ZrO2 catalysts for NO removal by CO using a rotary reactor

Abstract

The effect of a ZrO₂ support on the activity and adsorption behavior of Cu/Fe₂O₃–CeO₂/ZrO₂ catalysts was investigated by BET, XRD, SEM, Raman, H₂-TPR and XPS. The NO removal performance of these catalysts in a rotary reactor at 150 °C was correlated with their catalytic activity for NO + CO, and the surface processes occurring upon NO + O₂ interaction with the catalysts were studied by in situ DRIFTS. The results showed that the doping of suitable amounts of ceria into the zirconia lattice would lead to contraction of its lattice and an increase in bulk defects, which could promote the oxygen mobility and enhance the interaction between Cu/Fe₂O₃–CeO₂/ZrO₂ and ZrO₂. The ZrO₂ support could increase the concentration of oxygen vacancies, which could promote the dissociation of oxygen molecules and increase the activity for NO oxidation. The surface oxygen contributed to the conversion of NO₂ into stable nitrates and the low concentration of surface oxygen promoted the formation of labile nitrites. The remarkably high NO removal efficiency was attributed to the significantly enhanced adsorption of unstable adsorbed NO_x species (i.e., free nitrate ions and nitrosyl) and diminished stable adsorbed NO_x species (i.e., bidentate nitrate and bridged nitrate) via Cu/Fe₂O₃–CeO₂/ZrO₂ support interactions.