Ag-loaded CeO2 catalysts for soot and C3H6 oxidation: Effect of Ag/Ce3+ on oxygen vacancies

A series of Ag-loaded Ag-CeO2 catalysts (4.5, 6.5, 8.5 wt%) were prepared by incipient wetness impregnation method for soot and C3H6 oxidation based on the thermogravimetric analyzer and fixed-bed tubular reactor. Meanwhile, the structural properties and electronic states of the catalysts have been studied by nitrogen adsorption and desorption, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Compared with pure soot combustion, the Ag loading of 8.5 wt% reduced the temperature at which the soot reached the maximum weight loss rate from 630 °C to 278 °C and effectively reduced the activation energy of soot from 171.44 KJ/mol to 26.33 KJ/mol. The study indicates that Ag-CeO2 has better catalytic activity at Ag loading of about 8.5 wt%. The result of C3H6 oxidation showed that the participation of Ag-CeO2 reduced the ignition temperature of C3H6 by more than 50 °C and increased the conversion by 36.1 %. The temperature range of NO/NO2 change during the oxidation of C3H6 was concentrated between 250 °C and 345 °C. In addition, the characterization of the catalysts showed that Ag(8.5)-CeO2 had the highest Ag/Ce3+ ratio of 0.43 and the highest number of oxygen vacancies, indicating that the high Ag/Ce3+ atomic ratio may enhance the generation of oxygen vacancies on the Ag-CeO2 surface. This work helps demonstrate the oxidation performance of Ag-CeO2 on soot and C3H6 as well as to prepare highly active Ag-CeO2.