Method for the selective catalytic reduction of nitrogen...

Details Method for the selective catalytic reduction of nitrogen... Method for the selective catalytic reduction of nitrogen...

2007-12-20

2011-11-01

Mayes, Melvin (Department: 1732)

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Group ib metal

C423S213200, C423S237000, C423S352000

Reexamination Certificate

active

08048390

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.

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