Promotional effect of Nb additive on the activity and hydrothermal stability for the selective catalytic reduction of NOx with NH3 over CeZrOx catalyst.

The promotional mechanism of Nb addition on the activity and hydrothermal stability of CeZr 2 O x catalyst for the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) was investigated by various methods including N 2 -physisorption, XRD, H 2 -TPR and in situ DRIFTS. The Nb-promoted CeZr 2 O x catalyst showed remarkable NH 3 -SCR activity together with excellent N 2 selectivity, SO 2 /H 2 O resistance and outstanding hydrothermal stability. The characterization results showed that the introduction of Nb to CeZr 2 O x not only resulted in the high surface area and strong redox ability, but also promoted the adsorption and activation of NH 3 and enhanced the reactivity of adsorbed nitrate together with NH 3 species. All the above features were favorable for the superior NH 3 -SCR performance. In addition, the CeNb 3.0 Zr 2 O x catalysts hydrothermally aged below 800 °C still possessed high redox ability and abundant acid sites, all of which were responsible for the excellent hydrothermal durability. The novel CeNb 3.0 Zr 2 O x catalyst was a promising candidate for the removal of NO x from diesel engine. [ABSTRACT FROM AUTHOR]