Comparative study of 3D ordered macroporous Ce0.75Zr0.2M0.05O2−δ (M = Fe, Cu, Mn, Co) for selective catalytic reduction of NO with NH3

Abstract

The three dimensional ordered macroporous (3DOM) Ce_0.75Zr_0.2M_0.05O_2−δ (M = Fe, Cu, Mn, Co) is synthesized by a colloidal crystal template method for comparative study on selective catalytic reduction (SCR) of NO with NH₃. The obtained catalysts are mainly investigated by the measurements of X-ray diffraction (XRD), N₂ sorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H₂-TPR), as well as temperature-programmed desorption of ammonia (NH₃-TPD). The XRD, XPS and TPR analysis clarified the dopants are effectively doped into the Ce–Zr oxide solid solution, which contribute to the strong synergistic effect between the dopants and Ce–Zr oxides. Moreover, higher O_α/(O_α + O_β) ratio, improved surface reducibility and enhanced surface acidity are observed after the in situ doping. These facts lead to a better low temperature catalytic performance for the Ce_0.75Zr_0.2M_0.05O_2−δ catalysts. Particularly, the Co doped catalysts exhibit the highest active oxygen species, the highest reducibility as well as the strongest NH₃ absorption ability, which corresponds to the significant increase of low temperature activity. Meanwhile, the specific surface area and pore volume are increased efficiently by Fe and Mn doping, which broadens the operating temperature window. Moreover, the strong interaction between the dopants and the Ce–Zr oxide solid solution could be ascribed to the good stability of those catalysts doped with Fe, Mn and Co.