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

US5785937A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Ronald Neufert · Aichach, DE
• Wieland Mathes · Aichach, DE
• Dagmar Schobert-Schaefer · Hersbruck, DE
• Lothar Hofmann · Burgkunstadt, DE

Key dates

• Filing date: Feb 10, 1997
• Grant date: Jul 28, 1998
• Expiry date: Feb 10, 2017

Classification

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

Abstract

A method is provided in which the reducing agent, during the starting phase of the internal-combustion engine and during operation with decreasing and, if appropriate, virtually constant exhaust gas temperature, is fed superstoichiometrically in relation to the nitrogen oxide concentration, while taking into account the temperature-dependent storage capacity of a denitration catalytic converter for the reducing agent. The reducing agent is otherwise fed substoichiometrically. In this manner, the catalytic converter is kept at all times at a preferred charge level, so that on one hand it is possible to provide sufficient stored reducing agent for the catalytic conversion and on the other hand it is possible to still have a reducing agent buffer available which avoids slip of the reducing agent. The invention can be used in all internal-combustion engines operated with air excess, such as diesel engines and lean-burn engines.