Effect of Reductants on the NOx Storage Performance of a Pd/CZO Low Temperature NOx Adsorber

摘要: Low temperature NOx adsorbers (LTNA) adsorb the emissions from diesel engines during cold start period and then thermally release when downstream urea SCR system is operational. A degreened monolithic core sample of a LTNA with palladium on ceria-zirconia washcoat (Pd/CZO) was evaluated for storage performance under lean conditions using reactor-based transient test without different reductants [i.e., ethylene (C2H4), carbon monoxide (CO), hydrogen (H2), or 3:1 CO:H2 mix]. Relative to tests reductant, all four increased amount stored LTNA. The decreased gradually consecutive tests. Lean methane (CH4) oxidation used probe average state PdOx in after reduced similarly NO alone each reductant but significantly less alone. by reacting form NO2 between 200 210 °C. CH4 were also performed bed exceeded 185 °C (i.e., period). There little reduction alone, there significant similar reductant. This supported mechanism where interacted chemical intermediate site, reducing process. determined as function time reductants. CO CO/H2 more rapidly than C2H4 H2, which correlated superior CO/H2. It proposed that responsible gradual drop efficiency Consistent that, maximum could be recovered oxidizing catalyst 700 750 °C. Future work includes assessment zeolite-based LTNAs are sulfur tolerant ceria-based LTNAs.