Mn-Fe-Ce multiple oxides with Al2O3 coating supported onto honeycomb cordierite monoliths for NO catalytic oxidation.

Mn-Fe-CeOx-Al 2 O 3 /HCM catalyst have the potential advantages of good catalytic activity, appropriate production process and moderate shedding rate with shedding modes of internal and interface spalling, comparing to the Mn-Fe-CeOx/Al 2 O 3 /HCM sample. • Mn-Fe-CeOx-Al 2 O 3 /HCM, Mn-Fe-CeOx/Al 2 O 3 /HCM and Mn-Fe-CeOx/HCM were compared for NO oxidation. • Al 2 O 3 -coatings increased surface area and active-components loadings for better enhancement. • Mn-Fe-CeOx-Al 2 O 3 /HCM have good catalytic activity, appropriate production process and moderate shedding rate. • Promoted NO-to-NO 2 via intermediate nitrate-species were benefited from more active oxygen. • Mn-Fe synergetic interaction and Ce-accelerated electron cycles were favorable for catalytic activity. Mn-Fe-Ce multiple oxides with Al 2 O 3 coating supported over honeycomb cordierite monoliths including Mn-Fe-CeOx/Al 2 O 3 /HCM and Mn-Fe-CeOx-Al 2 O 3 /HCM were optimized and compared for the catalytic oxidation of NO. The addition of Al 2 O 3 -coatings increased the specific surface area for more loadings of active components and also making the distribution of active species more uniform. Pseudo-boehmite as coating showed a better enhancement on NO oxidation than nano-Al 2 O 3 coating directly. Whatever Mn-Fe-CeOx/Al 2 O 3 /HCM prepared by sol-gel and impregnation methods or Mn-Fe-CeOx-Al 2 O 3 /HCM prepared by slurry coating of co-precipitated Mn-Fe-CeOx powders and pseudo-boehmite binders onto HCM, the optimized doping amounts of Mn-Fe-CeOx was 15 wt. % with 10 wt. % Al 2 O 3 for good activity than the impregnated Mn-Fe-CeOx/HCM without Al 2 O 3 -coatings. H 2 -TPR, SEM, XPS, NO + O 2 -TPD and DRIFTS characterizations showed that the promoted catalytic oxidation activity of NO-to-NO 2 via the intermediate nitrate-species over Mn-Fe-CeOx/Al 2 O 3 /HCM and Mn-Fe-CeOx-Al 2 O 3 /HCM were benefited from more surface concentrations of active oxygen, efficient synergetic interaction between Fe and Mn ions (Fe2+ + Mn4+ ↔ Mn3+ + Fe3+) and high oxidizing ability accelerated by high Ce4+/Ce3+ ratio. Mn-Fe-CeOx-Al 2 O 3 /HCM catalyst have the potential advantages of good catalytic activity (74.4 % NO conversion at 250 °C) and appropriate production process (3−4 days of preparation period), which also gave the moderate shedding rate with the shedding modes of internal spalling and interface spalling than Mn-Fe-CeOx/Al 2 O 3 /HCM sample. [ABSTRACT FROM AUTHOR]