(735e) Abatement of Diesel Soot Under Various Catalyst/Soot Contact Conditions

When investigating metal oxides in graphite oxidation, McKee for the first time, pointed out that the activity of an oxide depends more on the localized interaction between catalyst and carbon than on the thermodynamic properties of oxides. The former was latterly referred as “contact condition” in diesel soot oxidation, and it is widely accepted that the reported performances in literature for soot oxidation catalysts are strongly affected by “contact condition”, exhaust composition and the nature of the soot used in the experiments. It is thus often difficult to compare the performances of these catalysts without assessing various factors affecting the catalytic performance. For this reason, during the evaluation of a novel K-containing glass soot oxidation catalyst [1], present study investigated in an attempt to understand the effects of various contact conditions on soot oxidation.

Konstandapoulus et al. developed a two-layer soot oxidation model to describe the effect of catalyst coating of porous filter taking explicitly into account the soot-catalyst contact. Catalytic zone was defined as a region over which a spatial “field of catalyst activity” exists, and soot particles oxidize within the “field of activity” are considered in contact with the catalyst. Non-catalytic zone is formed by soot particles which form a “queue” on top of the filled-up catalyst affected layer. In present study, the content of SOF/VOF in engine soot is not negligible, and soot oxidation TGA curves indicated that catalyst also plays a role on SOF/VOF oxidation by decreasing SOF/VOF ignition temperature by 250 oC. An additional type of soot oxidation presenting SOF/VOF in soot particle was defined. Consequently, catalytic soot oxidation on coated wire mesh can be subdivided to three zones, namely, zone I for SOF/VOF oxidation, zone II for catalytic soot oxidation (by O2), and zone III for thermal soot oxidation.

For implementation of continuous DPF regeneration, this present model can applied by a balance temperature analysis while soot accumulation and soot oxidation reaching equilibrium. Due to high soot capacity with tight contact, Zone II of catalytic soot oxidation on wire mesh was employed and its comparison with non-catalytic soot oxidation was analyzed.