Zoned Exhaust System

摘要

A catalytic article having a flow-through substrate having an inlet, an outlet, and an axial length; an SCR zone containing a first SCR catalyst; and an oxidation zone containing (a) an ASC zone and a DOC zone or (b) a mixed ASC and DOC zone, where the oxidation zone contains an ammonia oxidation catalyst and a DOC catalyst, the SCR zone is positioned on the substrate from the inlet end and extends less than the axial length of the substrate from the inlet, the DOC zone or the mixed ASC and DOC zone is position on the substrate from the outlet end, and when the DOC zone is present, the ASC zone is located between the SCR zone and the DOC zone. In other catalytic articles, the ASC zone further comprises a DEC catalyst. Methods of using the catalytic articles in an SCR process, where the amount of ammonia slip is reduced, are also described.

主权项

1. A catalytic article comprising
i a flow-through substrate having an inlet, an outlet, and an axial length; ii an SCR zone having a first SCR catalyst and being positioned on the substrate from the inlet to less than the axial length of the substrate; and iii and an oxidation zone comprising a PGM-containing ammonia oxidation catalyst and a PGM-containing DOC catalyst wherein, the PGM-containing ammonia oxidation catalyst and the PGM-containing DOC catalyst are arranged in (a) an ASC zone and a separate DOC zone or (b) a mixed ASC and DOC zone, wherein the DOC zone or the mixed ASC and DOC zone is positioned on the substrate from the outlet end to less than the axial length of the substrate, and when the separate DOC zone is present, the ASC zone is located between the SCR zone and the DOC zone,
provided that the DOC catalyst has a higher concentration (grams per cubic liter) of PGM relative to the ammonia oxidation catalyst.