Composition-Dependent Performance of CexZr1–xO2Mixed-Oxide-Supported WO3Catalysts for the NOxStorage Reduction–Selective Catalytic Reduction Coupled Process

Abstract

WO3/CexZr1–xO2 materials were evaluated as a possible NH3-selective catalytic reduction (SCR) active catalyst in a NOx storage reduction (NSR) + SCR combined system. The effect of the support composition was investigated at a constant WO3 loading (9.1 wt % of WO3). The impact of WO3 promotion over textural, structural, acid–base, and redox properties of SCR samples was characterized by means of nitrogen adsorption–desorption isotherms, XRD, NOx storage capacity, NH3 temperature programmed desporption, pyridine adsorption followed by FTIR, and H2-TPR. Catalytic activities in NH3-SCR and NH3-SCO reactions as well as corresponding kinetics parameters are also discussed. All WO3/Ce–Zr materials are active and fully selective in N2 for NOx reduction by NH3 and ammonia oxidation by O2. For the SCR reaction, the rate of NO conversion is found approximately half-order with respect to NO, and negative to nearly zero-order with respect to NH3. Tungstated ceria–zirconia materials were then associated downstream with...