Method for the reactivation of thermally aged nitrogen oxide storage catalytic converters

US7638452B2 · kind B2 · utility

Assignee

• UMICORE AG & CO. KG · DE

Inventors

• Meike Wittrock · Bensberg, DE
• Ulrich Goebel · Hattersheim, DE
• Thomas Kreuzer · Karben, DE
• Christina Maria Casapu · Waldshut-Tiengen, DE
• Jan-Dierk Grunwaldt · Avenue Madeleine, DK
• Marek Maciejewski · Warszawa, PL
• Alfons Baiker · Opfikon, CH

Key dates

• Filing date: Jul 15, 2006
• Grant date: Dec 29, 2009
• Expiry date: Jul 15, 2026

Classification

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

Abstract

Nitrogen oxide storage catalysts are used for removing the nitrogen oxides present in the lean-burn exhaust gas of lean-burn engines. Here, the purifying action is based on the nitrogen oxides being stored in the form of nitrates by the storage material of the storage catalyst during a lean-burn operating phase of the engine and the previously formed nitrates being decomposed in a subsequent rich-burn operating phase of the engine and the nitrogen oxides which are being liberated again being reacted with the reducing exhaust gas constituents over the storage catalyst to form nitrogen, carbon dioxide and water. Storage catalysts are thermally aged by high temperatures. The aging is due to sintering of the catalytically active noble metal components of the catalyst and to formation of compounds of the storage components with the support materials. According to the invention, the formation of compounds of the storage materials can be largely reversed by treatment of the storage material with a gas mixture comprising nitrogen dioxide and/or carbon dioxide and water vapor at temperatures of from 300 to 500° C. The reactivation can be carried out either directly on the vehicle by setting…