Highly dispersed CeO2on carbon nanotubes for selective catalytic reduction of NO with NH3

Abstract

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 (H2-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 Oα/(Oα + Oβ) 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 °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 °C with a desirable N2 selectivity. Moreover, the NO conversion can be kept at about 97% with the presence of SO2 or H2O at 300 °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 °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 Oα/(Oα + Oβ) ratio could be ascribed to the excellent NH3-SCR performance of the catalyst prepared by the pyridine-thermal route.