Synthesis and catalytic properties of CeO2 and Co/CeO2 nanofibers for diesel soot combustion

CeO2 nanofibres have been prepared by means of the co-precipitation and ripening method. The morphology of the CeO2 and the synthesis duration were influenced by changes in the mole ratio of the NaOH/citric acid. Three kinds of precipitates were obtained by increasing the NaOH/citric acid ratio: stuck-in-bundle, fibre and flake morphologies. The cobalt was impregnated on the prepared CeO2 (0.8) nanofibres and the physico-chemical properties, soot combustion activities and deactivation were investigated. The Co/CeO2 (0.8) nanofibres were evaluated for soot combustion in O2 and NO/O2. The morphology of the fibrous structure of CeO2 (0.8) and Co/CeO2 (0.8) was observed through FE SEM images. The presence of cobalt in Co3O4 form was confirmed by means of XRD and TPR analyses. The Co/CeO2 (0.8) fibre catalysts showed improvements in soot combustion at low temperatures of around 400 ◦C with 10% O2 and a decrease in the peak soot combustion temperature at about 40 ◦C was observed with the addition of 500 ppm NO. The XPS results of the Co 2p spectra of the Co/CeO2 (0.8) catalysts confirmed the presence of Co in the Co3+, Co2+ oxidation states. The thermal stability and the resistance to SO2 poisoning of the 10% Co/CeO2 (0.8) fibre catalyst were examined by ageing it in air and 1030 ppm SO2 at 800 ◦C for 12 h.