Process for operating an exhaust gas treatment unit containing a sulfur trap and a nitrogen oxides storage catalyst

US6145303A · kind A · utility

Assignee

• Degussa-Huels AG · DE

Inventors

• Wolfgang Strehlau · Großkrotzenburg, DE
• Ulrich Göbel · Hattersheim, DE
• Egbert Lox · Hanau, DE
• Wilfried Muller · Mannenberg, DE
• Rainer Domesle · Alzenau, DE

Key dates

• Filing date: Mar 25, 1999
• Grant date: Nov 14, 2000
• Expiry date: Mar 25, 2019

Classification

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

Abstract

A process is disclosed for operating an exhaust gas treatment unit for an internal combustion engine which is operated with lean normalized air/fuel ratios over most of the operating period. The exhaust gas treatment unit contains a nitrogen oxides storage catalyst with an activity window .DELTA.T.sub.NOX for the storage of nitrogen oxides at normalized air/fuel ratios of greater than 1 and release of the nitrogen oxides at normalized air/fuel ratios of less than or equal to 1 and a sulfur trap, located upstream of the nitrogen oxides storage catalyst, with a sulfur desorption temperature T.sub.S,DeSOx above which the sulfates stored on the sulfur trap are decomposed at normalized air/fuel ratios of less than or equal to 1. The nitrogen oxides contained in the exhaust gas are stored on the nitrogen oxides storage catalyst and the sulfur oxides are stored on the sulfur trap at normalized air/fuel ratios greater than 1 and exhaust gas temperatures T.sub.K within the activity window T.sub.NOX, wherein at the same time the exhaust gas temperature just upstream of the sulfur trap is lower than its sulfur desorption temperature T.sub.S,DeSOx. By cyclic lowering of the normalized air/fuel…