Catalytic oxidation of diesel particulate matter by using silver and ceria supported on alumina as the oxidation catalyst

Abstract To enable passive regeneration of a diesel particulate filter (DPF), this work seeks to study the potential of silver and ceria for the catalytic oxidation of diesel particulate matter (PM). Different contents of silver and ceria supported on alumina and silver loaded on ceria are synthesised by the incipient wetness impregnation method. The catalysts are characterised via XRD, SEM, and EDX. Catalytic PM oxidation performance for different PM/catalyst weight ratios and contact conditions is examined by using TGA. Removal of light soluble organic fraction (SOF) occurs between 110 and 350 °C through the vaporisation process. For the PM/catalyst weight ratio of 1/5, the silver compositions do not improve the depletion of light SOF but promote the combustion of both heavy SOF and soot, and the enhancement increases with silver content. For 16 wt% of silver supported on alumina, the PM/catalyst weight ratio of 1/20, and tight contact, oxidative activity is improved throughout the temperature window for light and heavy SOF and soot. The silver catalyst shows good stability for five runs. Active oxygen adspecies generated by ceria are different from those produced by silver. Enhanced performance for light SOF oxidation at a relatively low temperature is obtained using pure ceria. With the addition of alumina into ceria, light SOF removal ability of ceria is negatively affected. The positive effect on heavy SOF and soot reduction gained from the presence of silver is suppressed when ceria is mixed with silver.