Nitrogen oxide storage catalyst

US6413904B1 · kind B1 · utility

Assignee

• OMG AG & Co. KG · DE

Inventors

• Wolfgang Strehlau · Großkrotzenburg, DE
• Ulrich Göbel · Hattersheim, DE
• Rainer Domesle · Alzenau, DE

Key dates

• Filing date: Oct 13, 1999
• Grant date: Jul 2, 2002
• Expiry date: Oct 13, 2019

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B01D2255/407
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

A nitrogen oxide storage catalyst which contains at least one catalyst material and at least one nitrogen oxide storage component from the group of alkali and alkaline earth metals. The nitrogen oxide storage component, after completing catalyst preparation, is present as finely divided barium sulfate, strontium sulfate, a mixture or mixed crystals of the two sulfates, or as their complete or incomplete decomposition product with an average particle size of less than 1 &mgr;m. Barium sulfate and/or strontium sulfate act as feed materials for the active storage component in the storage catalyst according to the invention. As a result of the reductive exhaust gas compositions occurring under normal automobile driving conditions barium sulfate and strontium sulfate decompose to compounds which are able to store nitrogen oxides. This compensates for the loss of active storage components which occurs due to aging. Barium sulfate and/or strontium sulfate may be decomposed during production by means of reductive calcination in order to obtain a high initial loading of the catalyst with storage compounds. In this case, these sulfates are used as auxiliary agents in order to introduce the h…