2018 Volume 91 Issue 3 Pages 437-443
Soot oxidation over CeO2–ZrO2 (CZ) has been studied herein. The soot-CZ mixtures were observed under different contact conditions using transmission electron microscopy (TEM) and evaluated using thermogravimetric-differential thermal analysis (TG-DTA). These results indicate that the soot ignition temperature depends on the soot/CZ contact degree, and the soot oxidation rate depends on the soot/CZ contact area. The TEM observation of soot-CZ mixture quenched at T50 (50% soot conversion) indicates that soot oxidation occurs only at the soot/CZ interface. Furthermore, the soot oxidation under 18O2 flow and under He flow suggests that CZ lattice oxygen is a more active oxygen species than the adsorbed oxygen on the CZ. The CZ lattice oxygen mainly oxidizes soot; however, the adsorbed oxygen on the CZ surface does not oxidize soot at lower temperatures. Thus, the adsorbed oxygen oxidizes the reaction intermediates such as adsorbed CO on the CZ surface, which shows that CZ lattice is more active than the adsorbed oxygen.
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