Highly dispersed CeO2 on carbon nanotubes for selective catalytic reduction of NO with NH3

Highly dispersed CeO2 on carbon nanotubes (CNTs) is successfully prepared by a pyridine-thermal route for selective catalytic reduction (SCR) of NO with NH3. This catalyst is mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction by hydrogen (H-2-TPR), temperature-programmed desorption of ammonia (NH3-TPD) and X-ray photoelectron spectroscopy (XPS). The results of the XRD, TEM and TPR analysis show that the CeO2 particles on the CNTs are highly dispersed with a strong interaction between the particles and the CNTs. The NH3-TPD profiles indicate that this catalyst exhibits abundant strong acid sites. Furthermore, the O 1s XPS spectra show that the O-alpha/(O-alpha + O-beta) ratio of this catalyst is very high, which can result in more surface oxygen vacancies and therefore favor the NH3-SCR reaction. Compared with the catalysts prepared by impregnation or physical mixture methods, the catalyst prepared by the pyridine-thermal route presents the best NH3-SCR activity in the temperature range of 150-380 degrees C as well as favourable stability and good SO2 or H2O resistance. More than 90% of NO can be removed in the range of 250-370 degrees C with a desirable N-2 selectivity. Moreover, the NO conversion can be kept at about 97% with the presence of SO2 or H2O at 300 degrees C. In addition, this catalyst shows a high catalytic activity with a NO conversion remaining constant at ca. 98% during a 16 h continuous run duration at 300 degrees C. Highly dispersed CeO2 on the CNTs as well as the strong interaction between the particles and the CNTs, the large amounts of strong acid sites and the high O-alpha/(O-alpha + O-beta) ratio could be ascribed to the excellent NH3-SCR performance of the catalyst prepared by the pyridine-thermal route.