Nb-Modified CeAlOx Catalyst Used for the Selective Catalytic Reduction of NO by NH3: The Promoting Effect of Nb

Abstract

A series of Nb modified CeAlO_x catalysts were prepared by hydrothermal method and tested in the selective catalytic reduction of NO with NH₃. The catalyst with an Nb/Al molar ratio of 1 : 1 exhibited the best catalytic activity and high resistance to sulfur poisoning. Nitrogen adsorption measurements, XRD, NH₃-TPD, H₂-TPR and XPS analyses as well as in situ DRIFTS technique were applied to characterize the catalysts. The characterization results showed that the introduction of Nb enhanced the redox power and increased surface acidity. Moreover, the modification enriched the catalyst surface with adsorbed O_α and Ce³⁺ species. In addition, in situ DRIFTS experiments demonstrated that doping with Nb increased catalyst adsorption capacity for NH₃ while decreased the adsorption capacity for NO + O₂. All of these factors played important roles in improving NH₃-SCR performance of the modified catalysts.