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

Abstract

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 CsNO 3 . 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.

Catalytic Soot Combustion─General Concepts and Alkali Promotion

“…Another key issue in soot combustion testing is related to the type of catalyst–soot interparticle contacts. There are at least three different modes reported in the literature: Tight contact commonly applied because it is the most reproducible and the most informative about the actual catalyst activity, usually achieved by grinding in an agate mortar for a predetermined time, for example, 3, 6, 10, or 30 min, ,,,,,,,− ,,,,,, or sometimes by ball milling Loose contact the most resembling the real conditions, usually realized by gentle mixing of reagents with a spatula or in a vial. ,,,− ,− ,,,,,− ,− ,− Wet contact popular for monolithic catalysts, before deposition onto the catalyst soot is usually suspended in an organic solvent, e.g., ethanol ,, or n -penetene. ,, …”

Fe‐Ce Composite Oxide Catalysts Supported on 3D Nickel Foam for Catalytic Oxidation of Soot

“…At present, the catalysts used in CDPFs for soot elimination are mainly noble metal catalysts, alkali metal/alkali‐earth metal catalysts, transition metal catalysts and composite oxide catalysts [5–12] . Noble metal catalysts exhibit superior catalytic activity, but they cannot be widely used in industry owing to the scarcity and high price [13] .…”

“…At present, the catalysts used in CDPFs for soot elimination are mainly noble metal catalysts, alkali metal/alkali-earth metal catalysts, transition metal catalysts and composite oxide catalysts. [5][6][7][8][9][10][11][12] Noble metal catalysts exhibit superior catalytic activity, but they cannot be widely used in industry owing to the scarcity and high price. [13] The use of alkaline/alkaline earth metal catalysts could cause bad stability, and transition metals used alone could also give rise to poor catalytic activity for soot oxidation at low temperature.…”

Preparation of K Modified Three-Dimensionally Ordered Macroporous MnCeOx/Ti0.7Si0.3O2 Catalysts and Their Catalytic Performance for Soot Combustion

“…At present, owing to three-phase gas(O 2 )-solid(soot)-solid(catalyst) reaction for soot combustion, various catalysts were prepared to improve the contact efficiency between soot and catalyst [7,8]. Different morphologies of catalysts with nanotube array, nanobelt, nanofiber, nanowire, disordered macropore, and 3DOM structures are studied to enhance effective contact [9][10][11][12][13][14].…”