Process for the operation of a nitrogen oxides storage catalyst

US6171565A · kind A · utility

Assignee

• Degussa-Huels AG · DE

Inventors

• Jurgen Hohne · Hanau, DE
• Wolfgang Strehlau · Großkrotzenburg, DE
• Egbert Lox · Hanau, DE
• Thomas Kreuzer · Karben, DE

Key dates

• Filing date: Jan 8, 1999
• Grant date: Jan 9, 2001
• Expiry date: Jan 8, 2019

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02T10/40
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

A process of operating a nitrogen oxides storage catalyst of an exhaust gas treatment system is described. The process relates to the cycling of the normalized air/fuel ratio .lambda.-value of the exhaust gas exiting the engine, in which a lambda value greater than 1 represents oxygen-rich, lean burn conditions in which a sorption phase for the sorption of nitrogen oxides takes place; and in which a lambda value less than 1 represents oxygen-poor, rich burn conditions in which a desorption and conversion phase for the desorption and conversion of nitrogen oxides takes place. The .lambda.-value of the exhaust gas downstream from the storage catalyst is monitored during the desorption and conversion phase to determine the end of the desorption and conversion phase based on the .lambda.-value falling below a predetermined threshold value. Advantages of the process described include the ability to distinguish permanent from temporary damage to the nitrogen oxides storage catalyst, the ability to compensate for the slow deterioration in storage capacity, and the ability to determine when the storage capacity of the catalyst falls below a certain minimum capacity after which the storage …