A Co3O4–CeO2 functionalized SBA-15 monolith with a three-dimensional framework improves NOx-assisted soot combustion

Abstract

In this work, a cobalt and cerium composite oxide functionalized SBA-15 monolith (SM) with an inner three-dimensional (3D) network structure (CoCe/SM) was prepared by isovolumetric impregnation. Its catalytic activities towards NO_x-assisted soot combustion were evaluated and the loading and Co/Ce ratio were optimized. X-ray diffraction, scanning electron microscopy, energy dispersed spectroscopy, transmission electron microscopy, N₂ adsorption, X-ray photoelectron spectroscopy, H₂ temperature-programmed reduction and O₂ temperature-programmed desorption were employed to characterize the samples. It was revealed that, compared with unsupported Co₃O₄–CeO₂ particles, the CoCe/SM catalysts with optimized Co₃O₄–CeO₂ loading showed much higher catalytic ability, achieving a complete oxidation of the soot to CO₂ below 400 °C in the presence of NO_x, which is attributed to the high dispersion of Co₃O₄–CeO₂ on SM and the cross-linked macroporous structure of SM that can house the soot particulates, thus providing closer contact between the soot and catalytically active sites.