Exhaust gas treatment units for internal combustion engines and processes for operating them

US6725647B2 · kind B2 · utility

Assignee

• UMICORE AG & CO. KG · DE

Inventors

• Marcus Pfeifer · Mannheim, DE
• Barry Van Setten · Salmünster, DE
• Jurgen Gieshoff · Bad Orb, DE
• Paul Spurk · Weiterstadt, DE
• Egbert Lox · Hanau, DE
• Thomas Kreuzer · Karben, DE

Key dates

• Filing date: Jan 28, 2002
• Grant date: Apr 27, 2004
• Expiry date: Jan 28, 2022

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02T10/12
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

The present invention provides an exhaust gas treatment unit for an internal combustion engine. A first catalyst unit produces ammonia from corresponding constituents in a rich exhaust gas composition. A second catalyst unit that is located downstream of the first catalyst unit temporarily stores the ammonia produced by the first catalyst unit in the presence of a rich exhaust gas composition. In the presence of a lean exhaust gas composition, the nitrogen oxides present in the exhaust gas are subjected to a reduction reaction using the temporarily stored ammonia as reducing agent. The exhaust gas treatment unit also contains a third catalyst unit that is located between the other two catalyst units, and oxidizes the nitrogen oxides present in the exhaust gas at lean exhaust gas conditions to a such an extent that 25 to 75 vol. % of the nitrogen oxides entering the second catalyst unit consist of nitrogen dioxide.