Effect of Cs-Ce-Zr Catalysts/Soot Contact Conditions on Diesel Soot Oxidation

Cs-Ce-Zr catalysts with various weight ratios are prepared by the sol-gel method in this paper. The main crystalline phases were identified by X-ray diffraction. The activities of catalysts during soot combustion were tested by thermogravimetric and differential scanning calorimetry. The contact conditions of soot/catalysts (sintered at 450 and 380 °C, respectively, under loose and tight contact conditions) were observed by scanning electron microscopy to study the effect of contact conditions on catalytic activity, and it was determined that the catalytic activities under tight contact conditions are superior to those under loose contact conditions. However, the soot oxidation rate speeds up after the peak temperature of about 450 °C under loose contact conditions, which is due to the fact that the contact condition is enhanced by melting CsNO₃. The soot onset ignition temperature is lower for the catalysts with more Cs content under loose contact conditions. The minimum gaps of the soot onset ignition temperature and soot oxidation rates under the two contact conditions are 32 and 7 °C, which shows that the gap of catalytic activities under the respective contact conditions can be decreased by the formation of different crystalline phases.