MnOx-CeO2 supported on a three-dimensional and networked SBA-15 monolith for NOx-assisted soot combustion

This paper reports the preparation and characterization of MnOx-CeO2/SBA-15 monolith (MnCe/SM) catalysts for NOx-assisted soot combustion. The SM with a three-dimensional (3D) network structure was synthesized by a sol-gel method, in which the shearing force and the acidity of the solution were finely tuned to direct the formation and assembly of the primary particles. The MnCe/SM catalysts were further prepared by a facile isovolumetric impregnation method. The samples were characterized by nitrogen adsorption, scanning electron microscopy, energy dispersed spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, H-2 temperature-programmed reduction, O-2 temperature-programmed desorption, NO temperature-programmed desorption, and NO temperature-programmed oxidation. It is found that the MnOx-CeO2 nanoparticles were dispersed in the channels or/and on the outer surface of the SM support depending on the loading, and had a strong synergistic effect. The MnCe/SM catalysts with an appropriate MnOx-CeO2 loading showed much higher catalytic performance for soot combustion than that of the unsupported MnOx-CeO2 mixture. This is attributed to the combination of the MnOx-CeO2 active component with the 3D network structure of SM. The later not only provides large surface area and high accessibility for the soot particulates to the active sites, but also acts as a particulate filter.