Method for the selective catalytic reduction of nitrogen oxides in exhaust gases of vehicles

US8048390B2 · kind B2 · utility

Assignee

• Alzchem Trostberg GmbH · DE

Inventors

• Benedikt Hammer · Trostberg, DE
• Hans-Peter Krimmer · Burgkirchen an der Alz, DE
• Bernd Schulz · Radebeul, DE
• Eberhard Jacob · Krailling, DE

Key dates

• Filing date: Dec 20, 2007
• Grant date: Nov 1, 2011
• Expiry date: Dec 20, 2027

Classification

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

Abstract

The invention relates to a method for the selective catalytic reduction of nitrogen oxides using ammonia in exhaust gases of vehicles, whereby solutions of guanidine salts with an ammonia forming potential of between 40 and 850 g/kg, optionally in combination with urea and/or ammonia and/or ammonium salts, are catalytically decomposed in the presence of catalytically active, non-oxidation-active coatings of oxides selected from the group containing titanium dioxide, aluminum oxide, silicon dioxide or the mixtures thereof, and hydrothermally stable zeolites which are fully or partially metal-exchanged. The guanidine salts according to the invention enable a reduction of the nitrogen oxides by approximately 90%. Furthermore, said guanidine salts can enable an increase in the ammonia forming potential from 0.2 kg, corresponding to prior art, up to 0.4 kg ammonia per litre of guanidine salt, along with freezing resistance (freezing point below −25° C.). The risk of corrosion of the guanidine salt solutions used according to the invention is also significantly reduced compared to that of solutions containing ammonium formiate.