Rare earth ions (La, Nd, Sm, Gd, and Tm) regulate the catalytic performance of CeO_2/Al_2O_3 for NH_3-SCR of NO

摘要

A series CeO_2/Al_2O_3 catalysts was modified with rare earth element (La, Nd, Sm, Gd, and Tm) using extrusion method. The catalytic activities of the obtained catalysts were measured for the selective catalytic reduction (SCR) of NO with NH_3 to screen suitable addition of rare earth element. These samples were characterized by X-ray diffraction (XRD), N_2 adsorption (N_2-BET), NH_3 temperature-programmed desorption analyses (NH_3-TPD), H_2 temperature-programmed reduction (H_2-TPR), Raman spectra, pyridine adsorption Fourier-transform infrared (Py-IR) and X-ray photoelectron spectroscopy (XPS), respectively. Results showed that the CeO_2/Al_2O_3 exhibited excellent performance in resisting reactant poisoning caused by vapor and sulfur and the highest catalytic activity (98.35%) at 360 °C when the added Tm/Ce molar ratio is 0.10. The surface acidity of CeO_2/Al_2O_3 catalyst would be enhanced with the addition of rare earth ions. Consequently, rare earth ion was beneficial to catalytic activity at low temperatures and corresponded to similar law. Analysis revealed that the higher number of acid sites and the more Ce~(3+) were conductive to obtain the excellent NH_3-SCR activity.