Method for the catalytic conversion of nitrogen oxides contained in the exhaust gas of an internal combustion engine

US6470676B2 · kind B2 · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Winfried Dolling · Weißenbrunn, DE
• Lothar Hofmann · Burgkunstadt, DE

Key dates

• Filing date: Jul 19, 2001
• Grant date: Oct 29, 2002
• Expiry date: Jul 19, 2021

Classification

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

Abstract

A method is provided for the catalytic conversion of nitrogen oxides contained in the exhaust gas of an internal combustion engine. A reducing agent is added in a controlled manner upstream of a denitrification catalyst, as seen in exhaust gas flow direction, and in dependence on a nitrogen oxide concentration. The reducing agent is added in a superstoichiometric amount in relation to the nitrogen oxide content if an operating parameter and/or a value derived from the operating parameter falls below or exceeds a threshold value. The addition of the reducing agent is then terminated or continued in a substoichiometric manner. The invention provides a measure for obtaining an extremely high average nitrogen oxide conversion, especially under varying operating conditions of the internal combustion engine.