Pt–Ce-soot generated from fuel-borne catalysts: soot oxidation mechanism

Soot containing Ce-, Pt-, Pt–Ce-, Fe-, and Cu-fuel-borne catalysts is generated in a diesel engine, is characterised by XRD, and studied in oxidation with O2 and NO + O2 under various reaction conditions. Fe-, Pt–Ce- and Ce-soot are oxidised at lower temperature with O2, compared with Pt-soot, and the opposite trend is observed with NO + O2. NO is oxidised to NO2 more efficiently over Pt-soot and decreased the soot oxidation temperature by about 150 °C, compared with Ce-, Fe- or Pt–Ce-soot. On the other hand, NO2 is most efficiently utilised over the Pt–Ce- and Ce-soot. The soot oxidation under the different feed gas conditions demonstrates that nitrate species are involved in the oxidation of Ce- and Pt–Ce-soot. The oxidation species with the decreasing order of activity are: (1) nitrates, (2) NO2, (3) lattice oxygen, and (4) gas-phase oxygen. All the above species are involved in the oxidation of Pt–Ce-soot.